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  • Exploring In-memory OLTP Engine (Hekaton) in SQL Server 2014 CTP1

    The continuing drop in the price of memory has made fast in-memory OLTP increasingly viable. SQL Server 2014 allows you to migrate the most-used tables in an existing database to memory-optimised 'Hekaton' technology, but how you balance between disk tables and in-memory tables for optimum performance requires judgement and experiment. What is this technology, and how can you exploit it? Rob Garrison explains.

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  • SQL: empty string vs NULL value

    - by Jacek Prucia
    I know this subject is a bit controversial and there are a lot of various articles/opinions floating around the internet. Unfortunatelly, most of them assume the person doesn't know what the difference between NULL and empty string is. So they tell stories about surprising results with joins/aggregates and generally do a bit more advanced SQL lessons. By doing this, they absolutely miss the whole point and are therefore useless for me. So hopefully this question and all answers will move subject a bit forward. Let's suppose I have a table with personal information (name, birth, etc) where one of the columns is an email address with varchar type. We assume that for some reason some people might not want to provide an email address. When inserting such data (without email) into the table, there are two available choices: set cell to NULL or set it to empty string (''). Let's assume that I'm aware of all the technical implications of choosing one solution over another and I can create correct SQL queries for either scenario. The problem is even when both values differ on the technical level, they are exactly the same on logical level. After looking at NULL and '' I came to a single conclusion: I don't know email address of the guy. Also no matter how hard i tried, I was not able to sent an e-mail using either NULL or empty string, so apparently most SMTP servers out there agree with my logic. So i tend to use NULL where i don't know the value and consider empty string a bad thing. After some intense discussions with colleagues i came with two questions: am I right in assuming that using empty string for an unknown value is causing a database to "lie" about the facts? To be more precise: using SQL's idea of what is value and what is not, I might come to conclusion: we have e-mail address, just by finding out it is not null. But then later on, when trying to send e-mail I'll come to contradictory conclusion: no, we don't have e-mail address, that @!#$ Database must have been lying! Is there any logical scenario in which an empty string '' could be such a good carrier of important information (besides value and no value), which would be troublesome/inefficient to store by any other way (like additional column). I've seen many posts claiming that sometimes it's good to use empty string along with real values and NULLs, but so far haven't seen a scenario that would be logical (in terms of SQL/DB design). P.S. Some people will be tempted to answer, that it is just a matter of personal taste. I don't agree. To me it is a design decision with important consequences. So i'd like to see answers where opion about this is backed by some logical and/or technical reasons.

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  • Is MongoDB a good choice or not for my application?

    - by shubham
    I have a Reporting application which stores the reports in xml format as recieved from source (XML schema is not defined, it can be any format) and those reports contain some keys and values. Like jobid, setid be keys for 1 type of report and userid, groupId for another type of report etc. The type of keys that can be referred from the document is determined by the namespaces used in the xml doc. These keys are stored on the basis of namespace used in the xml document. For e.g. If a tag in xml fragment uses namespace= "myspace1", then I have keys A and B for myspace1 stored in another table. It will fetch those keys from that table for this namespace, look for their values in xml doc and store it in another table along with the pointer to this xml document (Id of a record storing complete xml document in a cell). Use cases: When the user comes and queries for that key and value, I return the document or a set of documents that are having those key/value pairs. When the user comes and queries for a certain key and provide a name for xslt (pre stored), I fetch the set of documents fulfilling that criteria and convert that xml to html with the specified xslt. When the user comes and asks for a particular fragment of a doc then it can fetch a subset from a particular document also. When the user comes and queries for top x values of a certain key, I return the set of documents that are having top 10 values of that key. I am using DB2 database for its support of xml along with relational capabilities. That makes easier for me to run xpath expressions and fetch values of keys and also aggregate a set of documents fullfilling a criteria, all on the database side. Problems: DB2 stores XML doc of upto 2GB in size. Retrieval is very slow. If some thing involves many documents, then it takes significant time for things to show up in browser, and the user has to wait. Can MongoDb help in this case, as it is document oriented? can I do xml related xpath queries and document transformations on db side? Or is it ok to use both in such a case?

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  • What schema documentation tools exist for PostgreSQL

    - by Brad Koch
    MySQL has MySQL Workbench for designing and documenting your schema, and generates CREATE and ALTER scripts based on your design. We're looking at migrating to PostgreSQL in the near future, and we do need a practical way of documenting and modifying the schema structure. What similar tools exist for Postgres (that are OS X/Linux compatible)? Alternatively, what equivalent conventions would be followed for designing and documenting the structure of your Postgres database?

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  • Real-Time Multi-User Gaming Platform

    - by Victor Engel
    I asked this question at Stack Overflow but was told it's more appropriate here, so I'm posting it again here. I'm considering developing a real-time multi-user game, and I want to gather some information about possibilities before I do some real development. I've thought about how best to ask the question, and for simplicity, the best way that occurred to me was to make an analogy to the field (or playground) game darebase. In the field game of darebase, there are two or more bases. To start, there is one team on each base. The game is a fancy game of tag. When two people meet out in the field, the person who left his base most recently timewise captures the other person. They then return to that person's base. Play continues until everyone is part of the same team. So, analogizing this to an online computer game, let's suppose there are an indefinite number of bases. When a person starts up the game, he has a team that is located at, for example, his current GPS coordinates. It could be a virtual world, but for sake of argument, let's suppose the virtual world corresponds to the player's actual GPS coordinates. The game software then consults the database to see where the closest other base is that is online, and the two teams play their game of virtual tag. Note that the user of the other base could have a different base than the one run by the current user as the closest base to him, in which case, he would be in two simultaneous battles, one with each base. When they go offline, the state of their players is saved on a server somewhere. Game logic calls for the players to have some automaton-logic of some sort, so they can fend for themselves in a limited way using basic rules, until their user goes online again. The user doesn't control the players' movements directly, but issues general directives that influence the players' movement logic. I think this analogy is good enough to frame my question. What sort of platforms are available to develop this sort of game? I've been looking at smartfoxserver, but I'm not convinced yet that it is the best option or even that it will work at all. One possibility, of course, would be to roll out my own web server, but I'd rather not do that if there is an existing service out there already that I could tap into. I will be developing for iOS devices at first. So any suggestions would be greatly appreciated. I think I need to establish the architecture first before proceeding with this project. Note that darbase is not the game I intend to implement, but, upon reflection, that might not be a bad idea either.

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  • what is the best age for programmer to hire [on hold]

    - by Mohamed Ahmed
    I'm graduated from Information systems institute since 2004 and I worked as a ICDL Instructor , but I know some SQL Server good and Database Design , now I'm in 30 age , and I want to start study computer programming and get MCSA SQL Server and MCSE certificates , but I have feel I'm old to start and the companies will not accept me for that reason and also because I don't have any experience yet in the field , I will start like a fresh graduated in 21 or 22 age , please help me what is the best age for programmer for accepted , and the age and late start will be a big obstacle for me or not

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  • Speaking About SQL Server

    - by AllenMWhite
    There's a lot of excitement in the SQL Server world right now, with the RTM (Release to Manufacturing) release of SQL Server 2012 , and the availability of SQL Server Data Tools (SSDT) . My personal speaking schedule has exploded as well. Just this past Saturday I presented a session called Gather SQL Server Performance Data with PowerShell . There are a lot of events coming up, and I hope to see you at one or more of them. Here's a list of what's scheduled so far: First, I'll be presenting a session...(read more)

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  • 24 Hours of PASS next week, pre-con preview style

    - by drsql
    I will be doing my Characteristics of a Great Relational Database , which is a session that I haven’t done since last PASS. When I was asked about doing this Summit Preview version of 24 hours of PASS, I decided that I would do this session, largely because it is kind of light and fun, but also because it is either going to be the basis of the end section of my pre-con at the summit or it is going to be the section of the pre-con we don’t get to because we are so involved in working out designs that...(read more)

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  • Should I use multiple column primary keys or add a new colum?

    - by Covar
    My current database design makes use of a multiple column primary key to use existing data (that would be unique anyway) instead of creating an additional column assigning each entry an arbitrary key. I know that this is allowed, but was wondering if this is a practice that I might want to use cautiously and possibly avoid (much like goto in C). So what are some of the disadvantages I might see in this approach or reasons I might want a single column key?

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  • T-SQL Tuesday #016:Check Your Service Accounts with PowerShell

    - by AllenMWhite
    T-SQL Tuesday #016:Check Your Service Accounts with PowerShell This T-SQL Tuesday is about Aggregate Functions. It may be a bit of a stretch, but a security best practice to use separate service accounts for all your SQL Server services, so I've written some PowerShell code to check to see if any account is used more than once on a given machine. I take advantage of the SQLWmiManagement DLL to find the SQL Server services, which is a safer bet than filtering on a service name. First I load the SQLWmiManagement...(read more)

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  • Speaking About SQL Server

    - by AllenMWhite
    There's a lot of excitement in the SQL Server world right now, with the RTM (Release to Manufacturing) release of SQL Server 2012 , and the availability of SQL Server Data Tools (SSDT) . My personal speaking schedule has exploded as well. Just this past Saturday I presented a session called Gather SQL Server Performance Data with PowerShell . There are a lot of events coming up, and I hope to see you at one or more of them. Here's a list of what's scheduled so far: First, I'll be presenting a session...(read more)

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  • Should users be deleted after inactivity on a website?

    - by Hovaness Bartamian
    When you have a social website or a website where you can register, would you eventually delete them after a certain time (after a year of inactivity) or would you rather keep their account records for ever? I know websites like Facebook have large amount of inactive, duplicated and fake accounts. So I'm wondering if after two years of inactivity it would be alright to send the account a warning email of deletion unless they log in. Just thinking of a clean and efficient database management or any implications this may cause to new potential users.

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  • Speaking - SQL Saturday 173, Washington DC

    - by AllenMWhite
    After a great time at the PASS Summit in Seattle I'll be once again presenting on PowerShell for SQL Server at SQL Saturday #173 in Chevy Chase, Maryland. On Friday, December 7 I'll be presenting my full day session Automate and Manage SQL Server with PowerShell . Here's the abstract: This soup-to-nuts all day session will first introduce you to PowerShell, after which you'll learn the basic SMO object model, how to manipulate data with PowerShell and how to use SMO to manage objects. We'll then...(read more)

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  • Set and Verify the Retention Value for Change Data Capture

    - by AllenMWhite
    Last summer I set up Change Data Capture for a client to track changes to their application database to apply those changes to their data warehouse. The client had some issues a short while back and felt they needed to increase the retention period from the default 3 days to 5 days. I ran this query to make that change: sp_cdc_change_job @job_type='cleanup', @retention=7200 The value 7200 represents the number of minutes in a period of 5 days. All was well, but they recently asked how they can verify...(read more)

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  • Should I use multiple column primary keys or add a new column?

    - by Covar
    My current database design makes use of a multiple column primary key to use existing data (that would be unique anyway) instead of creating an additional column assigning each entry an arbitrary key. I know that this is allowed, but was wondering if this is a practice that I might want to use cautiously and possibly avoid (much like goto in C). So what are some of the disadvantages I might see in this approach or reasons I might want a single column key?

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  • Search For a Query in RDL Files with PowerShell

    - by AllenMWhite
    In tracking down poorly performing queries for clients I often encounter the query text in a trace file I've captured, but don't know the source of the query. I've found that many of the poorest performing queries are those written into the reports the business users need to make their decisions. If I can't figure out where they came from, usually years after the queries were written, I can't fix them. First thing I did was find a great utility called RSScripter , which opens up a Windows dialog...(read more)

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  • Collecting the Information in the Default Trace

    The default trace is still the best way of getting important information to provide a security audit of SQL Server, since it records such information as logins, changes to users and roles, changes in object permissions, error events and changes to both database settings and schemas. The only trouble is that the information is volatile. Feodor shows how to squirrel the information away to provide reports, check for unauthorised changes and provide forensic evidence.

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  • SQL Rally Voting Open

    - by AllenMWhite
    The voting for sessions for SQL Rally has been going on for a couple of weeks now. This week the Enterprise Database Administration & Deployment sessions are up for voting. I didn't go into politics because I don't feel comfortable telling people that they should vote for me but this is how the sessions are being decided for this conference, so here goes. I've submitted two abstracts, both grouped in the Summit Spotlight section. The first is a new session based on what I learned implementing...(read more)

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  • Preventing Problems in SQL Server

    It is never a good idea to let your users be the ones to tell you of database server outages. It is far better to be able to spot potential problems by being alerted for the most relevant conditions on your servers at the best threshold. This will take time and patience, but the reward will be an alerting system which allows you to deal more effectively with issues before they involve system down-time

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  • Should I have a separate method for Update(), Insert(), etc., or have a generic Query() that would be able to handle all of these?

    - by Prayos
    I'm currently trying to write a class library for a connection to a database. Looking over it, there are several different types of queries: Select From, Update, Insert, etc. My question is, what is the best practice for writing these queries in a C# application? Should I have a separate method for each of them(i.e. Update(), Insert()), or have a generic Query() that would be able to handle all of these? Thanks for any and all help!

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  • T-SQL Tuesday #015:Remaining on Alert

    - by AllenMWhite
    This T-SQL Tuesday is about Automation in SQL Server, and I'll bet you think I'm going to talk about PowerShell. Well, you're partially right. What I'd like to talk about today, though, is setting up alerts to automate some responses to naturally occuring phenomena on your SQL Servers. (Note: I first introduced this technique in an article on Simple Talk here ). Without going back to the original article, I'm talking about a safety valve process for when your transaction logs start to fill at rates...(read more)

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  • T-SQL Tuesday #015:Remaining on Alert

    - by AllenMWhite
    This T-SQL Tuesday is about Automation in SQL Server, and I'll bet you think I'm going to talk about PowerShell. Well, you're partially right. What I'd like to talk about today, though, is setting up alerts to automate some responses to naturally occuring phenomena on your SQL Servers. (Note: I first introduced this technique in an article on Simple Talk here ). Without going back to the original article, I'm talking about a safety valve process for when your transaction logs start to fill at rates...(read more)

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  • NoSQL vs Ehcache caching advise for speeding up read only mysql Database

    - by paddydub
    I'm building a Route Planner Webapp using Spring/Hibernate/Tomcat and a mysql database, I have a database containing read only data, such as Bus Stop Coordinates, Bus times which is never updated. I'm trying to make the app run faster, each time the application is run it will preform approx 1000 reads to the database to calculate a route. I have setup a Ehcache which greatly improves the read from database times. I'm now setting terracotta + Ehcache distributed caching to share the cache with multiple Tomcat JVMs. This seems a bit complicated. I've tried memcached but it was not performing as fast as ehcache. I'm wondering if a MongoDb or Redis would be better suited. I have no experience with nosql but I would appreciate if anyone has any ideas. What i need is quick access to the read only database.

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  • how to auto select the first index in a sparks List control in flex4

    - by james
    hi i have a spark List control. it has a dataProvider that shows reply from twitter search. i have created a function for change handler like this: protected function list_changeHandler(event:IndexChangeEvent):void { ta.text = coverflow.selectedItem.title; } so, whenever i select each of the items in the List i will see the message(ta.text) but now, instead of me manually clicking the first time, i want it to automatically click/select the first item and see the first message(ta.text) how do i do it? ... newbie to flex ... :p

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