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  • Designing a social network with CQRS, graph databases and relational databases in mind

    - by Siraj Mansour
    I have done quite an amount of research on the topic so far, but i couldn't come up with a conclusion to make up my mind. I am designing a social network and during my research i stumbled upon graph databases, i found neo4j pretty interesting for user relations and traversing through nodes. I also thought of using a relational database such as MS-SQL or MySQL to store entity data only and depending on neo4j for connections between entities. Of course this means more work in my application to store and pull data in and out of 2 different sources. My first question : Is using this approach (graph + relational) a good approach for designing my social network keeping in mind that users on social networks don't have to in synch with real data by split second ? What are the positives and negatives of this approach ? My Second question : I've been doing some reading on CQRS and as i understood it is mostly useful for collaborative environments, and environments where users see a lot of "stale" data. social networks has shared comments, events, etc .. and many users query or update the same data. Could CQRS be a helpful approach ? Would it give any performance/scalability benefits or non-useful complexity ? Is it fairly applicable with my possible choice of (graph + relational) databases approach mentioned in the question above ? My purpose is to know if the approaches i have mentioned above seem good enough for the business context.

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  • Big Data – Operational Databases Supporting Big Data – Key-Value Pair Databases and Document Databases – Day 13 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the Relational Database and NoSQL database in the Big Data Story. In this article we will understand the role of Key-Value Pair Databases and Document Databases Supporting Big Data Story. Now we will see a few of the examples of the operational databases. Relational Databases (Yesterday’s post) NoSQL Databases (Yesterday’s post) Key-Value Pair Databases (This post) Document Databases (This post) Columnar Databases (Tomorrow’s post) Graph Databases (Tomorrow’s post) Spatial Databases (Tomorrow’s post) Key Value Pair Databases Key Value Pair Databases are also known as KVP databases. A key is a field name and attribute, an identifier. The content of that field is its value, the data that is being identified and stored. They have a very simple implementation of NoSQL database concepts. They do not have schema hence they are very flexible as well as scalable. The disadvantages of Key Value Pair (KVP) database are that they do not follow ACID (Atomicity, Consistency, Isolation, Durability) properties. Additionally, it will require data architects to plan for data placement, replication as well as high availability. In KVP databases the data is stored as strings. Here is a simple example of how Key Value Database will look like: Key Value Name Pinal Dave Color Blue Twitter @pinaldave Name Nupur Dave Movie The Hero As the number of users grow in Key Value Pair databases it starts getting difficult to manage the entire database. As there is no specific schema or rules associated with the database, there are chances that database grows exponentially as well. It is very crucial to select the right Key Value Pair Database which offers an additional set of tools to manage the data and provides finer control over various business aspects of the same. Riak Rick is one of the most popular Key Value Database. It is known for its scalability and performance in high volume and velocity database. Additionally, it implements a mechanism for collection key and values which further helps to build manageable system. We will further discuss Riak in future blog posts. Key Value Databases are a good choice for social media, communities, caching layers for connecting other databases. In simpler words, whenever we required flexibility of the data storage keeping scalability in mind – KVP databases are good options to consider. Document Database There are two different kinds of document databases. 1) Full document Content (web pages, word docs etc) and 2) Storing Document Components for storage. The second types of the document database we are talking about over here. They use Javascript Object Notation (JSON) and Binary JSON for the structure of the documents. JSON is very easy to understand language and it is very easy to write for applications. There are two major structures of JSON used for Document Database – 1) Name Value Pairs and 2) Ordered List. MongoDB and CouchDB are two of the most popular Open Source NonRelational Document Database. MongoDB MongoDB databases are called collections. Each collection is build of documents and each document is composed of fields. MongoDB collections can be indexed for optimal performance. MongoDB ecosystem is highly available, supports query services as well as MapReduce. It is often used in high volume content management system. CouchDB CouchDB databases are composed of documents which consists fields and attachments (known as description). It supports ACID properties. The main attraction points of CouchDB are that it will continue to operate even though network connectivity is sketchy. Due to this nature CouchDB prefers local data storage. Document Database is a good choice of the database when users have to generate dynamic reports from elements which are changing very frequently. A good example of document usages is in real time analytics in social networking or content management system. Tomorrow In tomorrow’s blog post we will discuss about various other Operational Databases supporting Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • SQL Server v.Next (Denali) : More on contained databases and "contained users"

    - by AaronBertrand
    One of the reasons for contained databases (see my previous post ) is to allow for a more seamless transition when moving a database from one server to another. One of the biggest complications in doing so is making sure that all of the logins are in place on the new server. Contained databases help solve this issue by creating a new type of user: a database-level user with a password. I want to stress that this is not the same concept as a user without a login , which serves a completely different...(read more)

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  • mysql show databases not showing databases that are in /opt/bitnami/mysql/data directory

    - by hgolov
    and thank you for taking the time to look at my question. I have an ebs-backed ec2 ubuntu server which is running but unreachable. ** There are very stupidly no recent backups ** I made a snapshot of the block, created a volume, spun up a new instance, attached the new volume. I see all the data from my site in the /opt/bitnami/mysql/data directory, but when I go into the mysql console, it shows only information_schema and test when I type show databases; How can I 'point' mysql to the correct folder? Thank you!

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  • Would a model like this translate well to a document or graph database?

    - by Eric
    I'm trying to understand what types of models that I have traditionally persisted relationally would translate well to some kind of NoSQL database. Suppose I have a model with the following relationships: Product 1-----0..N Order Customer 1-----0..N Order And suppose I need to frequently query things like All Orders, All Products, All Customers, All Orders for Given Customer, All Orders for Given Product. My feeling is that this kind of model would not denormalize cleanly - If I had Product and Customer documents with embedded Orders, both documents would have duplicate orders. So I think I'd need separate documents for all three entities. Does a characteristic like this typically indicate that a document database is not well suited for a given model? Generally speaking, would a document database perform as well as a relational database in this kind of situation? I know very little about graph databases, but I understand that a graph database handles relationships more performantly than a document database - would a graph database be suited for this kind of model?

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  • Big Data – Operational Databases Supporting Big Data – Columnar, Graph and Spatial Database – Day 14 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the Key-Value Pair Databases and Document Databases in the Big Data Story. In this article we will understand the role of Columnar, Graph and Spatial Database supporting Big Data Story. Now we will see a few of the examples of the operational databases. Relational Databases (The day before yesterday’s post) NoSQL Databases (The day before yesterday’s post) Key-Value Pair Databases (Yesterday’s post) Document Databases (Yesterday’s post) Columnar Databases (Tomorrow’s post) Graph Databases (Today’s post) Spatial Databases (Today’s post) Columnar Databases  Relational Database is a row store database or a row oriented database. Columnar databases are column oriented or column store databases. As we discussed earlier in Big Data we have different kinds of data and we need to store different kinds of data in the database. When we have columnar database it is very easy to do so as we can just add a new column to the columnar database. HBase is one of the most popular columnar databases. It uses Hadoop file system and MapReduce for its core data storage. However, remember this is not a good solution for every application. This is particularly good for the database where there is high volume incremental data is gathered and processed. Graph Databases For a highly interconnected data it is suitable to use Graph Database. This database has node relationship structure. Nodes and relationships contain a Key Value Pair where data is stored. The major advantage of this database is that it supports faster navigation among various relationships. For example, Facebook uses a graph database to list and demonstrate various relationships between users. Neo4J is one of the most popular open source graph database. One of the major dis-advantage of the Graph Database is that it is not possible to self-reference (self joins in the RDBMS terms) and there might be real world scenarios where this might be required and graph database does not support it. Spatial Databases  We all use Foursquare, Google+ as well Facebook Check-ins for location aware check-ins. All the location aware applications figure out the position of the phone with the help of Global Positioning System (GPS). Think about it, so many different users at different location in the world and checking-in all together. Additionally, the applications now feature reach and users are demanding more and more information from them, for example like movies, coffee shop or places see. They are all running with the help of Spatial Databases. Spatial data are standardize by the Open Geospatial Consortium known as OGC. Spatial data helps answering many interesting questions like “Distance between two locations, area of interesting places etc.” When we think of it, it is very clear that handing spatial data and returning meaningful result is one big task when there are millions of users moving dynamically from one place to another place & requesting various spatial information. PostGIS/OpenGIS suite is very popular spatial database. It runs as a layer implementation on the RDBMS PostgreSQL. This makes it totally unique as it offers best from both the worlds. Courtesy: mushroom network Tomorrow In tomorrow’s blog post we will discuss about very important components of the Big Data Ecosystem – Hive. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Big Data – Operational Databases Supporting Big Data – RDBMS and NoSQL – Day 12 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the Cloud in the Big Data Story. In this article we will understand the role of Operational Databases Supporting Big Data Story. Even though we keep on talking about Big Data architecture, it is extremely crucial to understand that Big Data system can’t just exist in the isolation of itself. There are many needs of the business can only be fully filled with the help of the operational databases. Just having a system which can analysis big data may not solve every single data problem. Real World Example Think about this way, you are using Facebook and you have just updated your information about the current relationship status. In the next few seconds the same information is also reflected in the timeline of your partner as well as a few of the immediate friends. After a while you will notice that the same information is now also available to your remote friends. Later on when someone searches for all the relationship changes with their friends your change of the relationship will also show up in the same list. Now here is the question – do you think Big Data architecture is doing every single of these changes? Do you think that the immediate reflection of your relationship changes with your family member is also because of the technology used in Big Data. Actually the answer is Facebook uses MySQL to do various updates in the timeline as well as various events we do on their homepage. It is really difficult to part from the operational databases in any real world business. Now we will see a few of the examples of the operational databases. Relational Databases (This blog post) NoSQL Databases (This blog post) Key-Value Pair Databases (Tomorrow’s post) Document Databases (Tomorrow’s post) Columnar Databases (The Day After’s post) Graph Databases (The Day After’s post) Spatial Databases (The Day After’s post) Relational Databases We have earlier discussed about the RDBMS role in the Big Data’s story in detail so we will not cover it extensively over here. Relational Database is pretty much everywhere in most of the businesses which are here for many years. The importance and existence of the relational database are always going to be there as long as there are meaningful structured data around. There are many different kinds of relational databases for example Oracle, SQL Server, MySQL and many others. If you are looking for Open Source and widely accepted database, I suggest to try MySQL as that has been very popular in the last few years. I also suggest you to try out PostgreSQL as well. Besides many other essential qualities PostgreeSQL have very interesting licensing policies. PostgreSQL licenses allow modifications and distribution of the application in open or closed (source) form. One can make any modifications and can keep it private as well as well contribute to the community. I believe this one quality makes it much more interesting to use as well it will play very important role in future. Nonrelational Databases (NOSQL) We have also covered Nonrelational Dabases in earlier blog posts. NoSQL actually stands for Not Only SQL Databases. There are plenty of NoSQL databases out in the market and selecting the right one is always very challenging. Here are few of the properties which are very essential to consider when selecting the right NoSQL database for operational purpose. Data and Query Model Persistence of Data and Design Eventual Consistency Scalability Though above all of the properties are interesting to have in any NoSQL database but the one which most attracts to me is Eventual Consistency. Eventual Consistency RDBMS uses ACID (Atomicity, Consistency, Isolation, Durability) as a key mechanism for ensuring the data consistency, whereas NonRelational DBMS uses BASE for the same purpose. Base stands for Basically Available, Soft state and Eventual consistency. Eventual consistency is widely deployed in distributed systems. It is a consistency model used in distributed computing which expects unexpected often. In large distributed system, there are always various nodes joining and various nodes being removed as they are often using commodity servers. This happens either intentionally or accidentally. Even though one or more nodes are down, it is expected that entire system still functions normally. Applications should be able to do various updates as well as retrieval of the data successfully without any issue. Additionally, this also means that system is expected to return the same updated data anytime from all the functioning nodes. Irrespective of when any node is joining the system, if it is marked to hold some data it should contain the same updated data eventually. As per Wikipedia - Eventual consistency is a consistency model used in distributed computing that informally guarantees that, if no new updates are made to a given data item, eventually all accesses to that item will return the last updated value. In other words -  Informally, if no additional updates are made to a given data item, all reads to that item will eventually return the same value. Tomorrow In tomorrow’s blog post we will discuss about various other Operational Databases supporting Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • How to execute T-SQL for several databases which names are stored on a table

    - by emzero
    Hey guys, so here's the deal. I have several databases (SqlServer 2005) on the same server with the same schema but different data. I have one extra database which has one table storing the names of the mentioned databases. So what I need to do is to iterate over those databases name and actually "switch" to each one (use [dbname]) and execute a T-SQL script. Am I clear? Let me give you an example (simplified from the real one): CREATE TABLE DatabaseNames ( Id int, Name varchar(50) ) INSERT INTO DatabaseNames SELECT 'DatabaseA' INSERT INTO DatabaseNames SELECT 'DatabaseB' INSERT INTO DatabaseNames SELECT 'DatabaseC' Assume that DatabaseA, DatabaseB and DatabaseC are real existing databases. So let's say I need to create a new SP on those DBs. I need some script that loops over those databases and executes the T-SQL script I specify (maybe stored on a varchar variable or wherever). Any ideas? Thanks!

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  • How to execute T-SQL for several databases whose names are stored in a table

    - by emzero
    Hey guys, so here's the deal. I have several databases (SqlServer 2005) on the same server with the same schema but different data. I have one extra database which has one table storing the names of the mentioned databases. So what I need to do is to iterate over those databases name and actually "switch" to each one (use [dbname]) and execute a T-SQL script. Am I clear? Let me give you an example (simplified from the real one): CREATE TABLE DatabaseNames ( Id int, Name varchar(50) ) INSERT INTO DatabaseNames SELECT 'DatabaseA' INSERT INTO DatabaseNames SELECT 'DatabaseB' INSERT INTO DatabaseNames SELECT 'DatabaseC' Assume that DatabaseA, DatabaseB and DatabaseC are real existing databases. So let's say I need to create a new SP on those DBs. I need some script that loops over those databases and executes the T-SQL script I specify (maybe stored on a varchar variable or wherever). Any ideas? Thanks!

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  • Looking for a good implementation that will access multiple databases simultaneously

    - by eibhrum
    I just want to find out if there's a good implementation (in C#/ASP.NET) on how to access my records from my different databases simultaneously. I have this simple application which suppose to search on these databases, then, display the record if a certain keyword is matched. I have like 5 databases (currently using MySQL) all in all and will be expanding it on the future (might be changing to SQL Server). I am fully aware on how to search on a single database, while I'm still learning how do it in multiple databases. Any tips, comments or suggestions?

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  • How does I/O work for large graph databases?

    - by tjb1982
    I should preface this by saying that I'm mostly a front end web developer, trained as a musician, but over the past few years I've been getting more and more into computer science. So one idea I have as a fun toy project to learn about data structures and C programming was to design and implement my own very simple database that would manage an adjacency list of posts. I don't want SQL (maybe I'll do my own query language? I'm just having fun). It should support ACID. It should be capable of storing 1TB let's say. So with that, I was trying to think of how a database even stores data, without regard to data structures necessarily. I'm working on linux, and I've read that in that world "everything is a file," including hardware (like /dev/*), so I think that that obviously has to apply to a database, too, and it clearly does--whether it's MySQL or PostgreSQL or Neo4j, the database itself is a collection of files you can see in the filesystem. That said, there would come a point in scale where loading the entire database into primary memory just wouldn't work, so it doesn't make sense to design it with that mindset (I assume). However, reading from secondary memory would be much slower and regardless some portion of the database has to be in primary memory in order for you to be able to do anything with it. I read this post: Why use a database instead of just saving your data to disk? And I found it difficult to understand how other databases, like SQLite or Neo4j, read and write from secondary memory and are still very fast (faster, it would seem, than simply writing files to the filesystem as the above question suggests). It seems the key is indexing. But even indexes need to be stored in secondary memory. They are inherently smaller than the database itself, but indexes in a very large database might be prohibitively large, too. So my question is how is I/O generally done with large databases like the one I described above that would be at least 1TB storing a big adjacency list? If indexing is more or less the answer, how exactly does indexing work--what data structures should be involved?

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  • Let MySQL users create databases, but allow access to only their own databases

    - by eikes
    I want to have multiple a MySQL users to be able to issue commands like CREATE DATABASE dbTest; But I also want each of these users to be able to see and access only their own databases. All I could find was how to either create the databases by a DBA and grant the privileges on this database to the specific user: GRANT ALL PRIVILEGES ON dbTest.* TO 'user'; or grant privileges on all databases to a user: GRANT ALL PRIVILEGES ON *.* TO 'user'; But neither is what I want, because it needs to scale and be secure.

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  • Databases supporting parallel processing across multiple servers

    - by David
    I need a database engine that can utilize multiple servers for processing a single SQL query in parallel. So far I know that this is possible with the some engines, though none of them are feasible for me either because of pricing or missing features. The engines currently known to me are: MS SQL (enterprise) DB2 (enterprise) Oracle (enterprise) GridSQL Greenplum

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  • Which databases support parallel processing across multiple servers?

    - by David
    I need a database engine that can utilize multiple servers for processing a single SQL query in parallel. So far I know that this is possible with the some engines, though none of them are feasible for me either because of pricing or missing features. The engines currently known to me are: MS SQL (enterprise) DB2 (enterprise) Oracle (enterprise) GridSQL Greenplum Which other engines have this feature? Do you have any experience with using this feature? Edit: I have now proposed a method for creating one myself. Any input is welcome. Edit: I have found another one: Informix Extended Parallel Server

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  • Best way to generate report using multiple databases

    - by Vinaaven
    Hi All, I am new to the reporting world. Wanted to know which is the right solution to about for generating a single report by querying for data from multiple databases. We are planning to use some reporting solution like Jasper Reports or BIRT. Generally the databases are going to be postgresql. Please do feel free to let me know about any other better solutions as well. Thanks.

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  • Symfony Jobeet Tutorial Day 3, databases.yml error

    - by Tony
    Hi all, I'm new to Symfony and I'm going through the Jobeet tutorial v1.4 for Doctrine. I am currently stuck on Day 3. I've followed all the instructions on configuring the database and building models and modules; however, when I try to access "http://localhost:8080/frontend_dev.php" I receive the following error: 'Configuration "config/databases.yml" does not exist or is unreadable.' My config/databases.yml file looks like this: all: doctrine: class: sfDoctrineDatabase param: dsn: 'mysql:host=localhost;dbname=jobeet' username: root password: mysecret Creating the tables and loading the fixtures seem to work fine after checking the database with phpmyadmin. Any help would be appreciated. Thank you!

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  • Microsoft Sql Server 2008 R2 System Databases

    For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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  • Microsoft Sql Server 2008 R2 System Databases

    For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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  • How to identify a particular entity's Session Factory with Fluent NHibernate and Multiple Databases

    - by Trevor
    I've already asked this question as part of an answer to another question ( see http://stackoverflow.com/questions/2655861/fluent-nhibernate-multiple-databases ) but thought it better to ask again here. My problem is this: I'm using Fluent NHibernate. My application uses multiple databases. Each database has its own entities registered (mapped) against it. The result is that have multiple Session Factories, each one relating to a single DB, and each 'containing' its own set of mapped entities. For loading entities I've created a generic Factory class that provides some standard load methods usable for any registered entity (in any DB). The problem is: The load methods need to use the correct session factory for the entity class I'm busy dealing with. How would I determine which session factory I need to use? I have all the Session Factories 'on hand' (and indexed by database name), I just need a way, knowing just the type of Entity I'm about to load, of choosing the right Session Factory to use. For example: public IBaseBusinessObject CreatePopulatedInstance(Type boType, Guid instanceKey) { IBaseBusinessObject result = null; ISessionFactory sessionFactory = GetSessionFactory(boType); using (ISession session = sessionFactory.OpenSession()) { using (session.BeginTransaction()) { result = (IBaseBusinessObject)session.Get(boType, instanceKey); } } return result; } What needs to go on in GetSessionFactory(boType) ? Thanks for reading!

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  • A list of Entity Framework providers for various databases

    - by Robert Koritnik
    Which providers are there and your experience using them I would like to know about all possible native .net Framework Entity Framework providers that are out there as well as their limitations compared to the default Linq2Entities (from MS for MS SQL). If there are more for the same database even better. Tell me and I'll be updating this post with this list. Feel free to add additional providers directly into this post or provide an answer and others (including me) will add it to the list. Entity Framework 1 Microsoft SQL Server Standard/Enterprise/Express Linq 2 Entities - Microsoft SQL Server connector DataDirect ADO.NET Data Providers Microsoft SQL Server CE (Compact Edition) Any provider? MySQL MySQL Connector (since version 6.0) - I've read about issues when using Skip(), Take() and Sort() in the same expression tree - everyone welcome to input their experience/knowledge regarding this. (NOTE: MySQL Connector/NET Visual Studio Integration is not supported in the Express Editions of Visual Studio, meaning you won't be able to view MySQL databases in the Database explorer window or add a MySQL data source via Visual Studio wizard dialog boxes. Some users may find that this limits their ability to use Entity Framework and MySQL within Visual Studio Express). Devart dotConnect for MySQL - similar issues to MySql's connector as I've read and both try to blame MS for it [these issues are supposed to be solved] SQLite Devart dotConnect for SQLite System.Data.SQLite PostgreSQL Devart dotConnect for PostgreSQL Npgsql Oracle Devart dotConnect for Oracle Sample Entity Framework Provider for Oracle - community effort project DataDirect ADO.NET Data Providers DB2 IBM Data Server Provider has EF support. Here are some limitations. DataDirect ADO.NET Data Providers Sybase Sybase iAnywhere DataDirect ADO.NET Data Providers Informix IBM Data Server Provider supports Informix Firebird ADO.NET Data Provider with EF support Provider Wrappers Tracing and Caching Providers for EF Entity Framework 4 (beta) Microsoft SQL Server Microsoft's Linq to Entities 4 - shipped with .net 4.0 and Visual Studio 2010; so far the only provider for EF4 MySQL Devart dotConnect for MySQL SQLite Devart dotConnect for SQLite PostgreSQL Devart dotConnect for PostgreSQL Oracle Devart dotConnect for Oracle

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  • Checking if your SIMPLE databases need a log backup

    - by Fatherjack
    Hopefully you have read the blog by William Durkin explaining why your SIMPLE databases need a log backup in some cases. There is a SQL Server bug that means in some cases databases are marked as being in SIMPLE RECOVERY but have a log wait type that shows they are not properly configured. Please read his blog for the full explanation and a great description of how to reproduce the issue. As part of our (William happens to be my Boss) work to recover our affected databases I wrote this small PowerShell script to quickly check our servers for databases that needed the attention that William details.  cls $Servers = “Server01″,”Server02″,”etc”,”etc” foreach($Server in $Servers){ write-host “************” $server “****************”     $server = New-Object Microsoft.sqlserver.management.smo.server $Server     foreach($db in $Server.databases){         $db | where {$_.RecoveryModel -eq “Simple” -and $_.logreusewaitstatus -ne “nothing”} | select name, LogReuseWaitStatus     } } If you get any results from this query then you should consult Williams blog for the details on what action you should take. This script does give out false positives if in some circumstances depending on how busy your databases are. Hopefully this will let you check your servers quickly and if you find any problems you can reference Williams blog to understand what you need to do.

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  • Extending Database-as-a-Service to Provision Databases with Application Data

    - by Nilesh A
    Oracle Enterprise Manager 12c Database as a Service (DBaaS) empowers Self Service/SSA Users to rapidly spawn databases on demand in cloud. The configuration and structure of provisioned databases depends on respective service template selected by Self Service user while requesting for database. In EM12c, the DBaaS Self Service/SSA Administrator has the option of hosting various service templates in service catalog and based on underlying DBCA templates.Many times provisioned databases require production scale data either for UAT, testing or development purpose and managing DBCA templates with data can be unwieldy. So, we need to populate the database using post deployment script option and without any additional work for the SSA Users. The SSA Administrator can automate this task in few easy steps. For details on how to setup DBaaS Self Service Portal refer to the DBaaS CookbookIn this article, I will list steps required to enable EM 12c DBaaS to provision databases with application data in two distinct ways using: 1) Data pump 2) Transportable tablespaces (TTS). The steps listed below are just examples of how to extend EM 12c DBaaS and you can even have your own method plugged in part of post deployment script option. Using Data Pump to populate databases These are the steps to be followed to implement extending DBaaS using Data Pump methodolgy: Production DBA should run data pump export on the production database and make the dump file available to all the servers participating in the database zone [sample shown in Fig.1] -- Full exportexpdp FULL=y DUMPFILE=data_pump_dir:dpfull1%U.dmp, data_pump_dir:dpfull2%U.dmp PARALLEL=4 LOGFILE=data_pump_dir:dpexpfull.log JOB_NAME=dpexpfull Figure-1:  Full export of database using data pump Create a post deployment SQL script [sample shown in Fig. 2] and this script can either be uploaded into the software library by SSA Administrator or made available on a shared location accessible from servers where databases are likely to be provisioned Normal 0 -- Full importdeclare    h1   NUMBER;begin-- Creating the directory object where source database dump is backed up.    execute immediate 'create directory DEST_LOC as''/scratch/nagrawal/OracleHomes/oradata/INITCHNG/datafile''';-- Running import    h1 := dbms_datapump.open (operation => 'IMPORT', job_mode => 'FULL', job_name => 'DB_IMPORT10');    dbms_datapump.set_parallel(handle => h1, degree => 1);    dbms_datapump.add_file(handle => h1, filename => 'IMP_GRIDDB_FULL.LOG', directory => 'DATA_PUMP_DIR', filetype => 3);    dbms_datapump.add_file(handle => h1, filename => 'EXP_GRIDDB_FULL_%U.DMP', directory => 'DEST_LOC', filetype => 1);    dbms_datapump.start_job(handle => h1);    dbms_datapump.detach(handle => h1);end;/ Figure-2: Importing using data pump pl/sql procedures Using DBCA, create a template for the production database – include all the init.ora parameters, tablespaces, datafiles & their sizes SSA Administrator should customize “Create Database Deployment Procedure” and provide DBCA template created in the previous step. In “Additional Configuration Options” step of Customize “Create Database Deployment Procedure” flow, provide the name of the SQL script in the Custom Script section and lock the input (shown in Fig. 3). Continue saving the deployment procedure. Figure-3: Using Custom script option for calling Import SQL Now, an SSA user can login to Self Service Portal and use the flow to provision a database that will also  populate the data using the post deployment step. Using Transportable tablespaces to populate databases Copy of all user/application tablespaces will enable this method of populating databases. These are the required steps to extend DBaaS using transportable tablespaces: Production DBA needs to create a backup of tablespaces. Datafiles may need conversion [such as from Big Endian to Little Endian or vice versa] based on the platform of production and destination where DBaaS created the test database. Here is sample backup script shows how to find out if any conversion is required, describes the steps required to convert datafiles and backup tablespace. SSA Administrator should copy the database (tablespaces) backup datafiles and export dumps to the backup location accessible from the hosts participating in the database zone(s). Create a post deployment SQL script and this script can either be uploaded into the software library by SSA Administrator or made available on a shared location accessible from servers where databases are likely to be provisioned. Here is sample post deployment SQL script using transportable tablespaces. Using DBCA, create a template for the production database – all the init.ora parameters should be included. NOTE: DO NOT choose to bring tablespace data into this template as they will be created SSA Administrator should customize “Create Database Deployment Procedure” and provide DBCA template created in the previous step. In the “Additional Configuration Options” step of the flow, provide the name of the SQL script in the Custom Script section and lock the input. Continue saving the deployment procedure. Now, an SSA user can login to Self Service Portal and use the flow to provision a database that will also populate the data using the post deployment step. More Information: Database-as-a-Service on Exadata Cloud Podcast on Database as a Service using Oracle Enterprise Manager 12c Oracle Enterprise Manager 12c Installation and Administration guide, Cloud Administration guide DBaaS Cookbook Screenwatch: Private Database Cloud: Set Up the Cloud Self-Service Portal Screenwatch: Private Database Cloud: Use the Cloud Self-Service Portal Stay Connected: Twitter |  Face book |  You Tube |  Linked in |  Newsletter

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  • Graph databases and Php

    - by stagas
    I want to use a graph database using php. Can you point out some resources on where to get started? Is there any example code / tutorial out there? Or are there any other methods of storing data that relate to each other in totally random/abstract situations? Very abstract example of the relations needed: John relates to Mary, both relate to School, John is Tall, Mary is Short, John has Blue Eyes, Mary has Green Eyes, query I want is which people are related to 'Short people that have Green Eyes and go to School' - answer John It is possible in MySQL but it would require a fixed set of attributes/columns for each item and a complex non-flexible query, instead I need every attribute to be an item by itself and instead of 'belonging' to something, to be 'related' to something.

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  • Graph-structured databases and Php

    - by stagas
    I want to use a graph database using php. Can you point out some resources on where to get started? Is there any example code / tutorial out there? Or are there any other methods of storing data that relate to each other in totally random/abstract situations? - Very abstract example of the relations needed: John relates to Mary, both relate to School, John is Tall, Mary is Short, John has Blue Eyes, Mary has Green Eyes, query I want is which people are related to 'Short people that have Green Eyes and go to School' - answer John - Another example: TrackA -> ArtistA -> ArtistB -> AlbumA -----> [ label ] -> AlbumB -----> [ A ] -> TrackA:Remix -> Genre:House -> [ Album ] -----> [ label ] TrackB -> [ C ] [ B ] Example queries: Which Genre is TrackB closer to? answer: House - because it's related to Album C, which is related to TrackA and is related to Genre:House Get all Genre:House related albums of Label A : result: AlbumA, AlbumB - because they both have TrackA which is related to Genre:House - It is possible in MySQL but it would require a fixed set of attributes/columns for each item and a complex non-flexible query, instead I need every attribute to be an item by itself and instead of 'belonging' to something, to be 'related' to something.

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  • How do Relational Databases Work Under the Hood?

    - by Pierreten
    I've always been interested in how you can throw some SQL at at database, and it nearly instantaneously returns your results in an orderly manner without thinking about it as anything other than a black box. What is really going on? I'm pretty sure it has something to do with how values are laid out regularly in memory, similar to an array; but aside from that, I don't know much else. How is SQL parsed in a manner to facilitate all of this?

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