Search Results

Search found 1155 results on 47 pages for 'relational algebra'.

Page 1/47 | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

  • Help to translate SQL query to Relational Algebra

    - by Mestika
    Hi everyone, I'm having some difficulties with translating some queries to Relational Algebra. I've a great book about Database Design and here is a chapter about Relational Algebra but I still seem to have some trouble creating the right one: Thoes queries I've most difficuelt with is these: SELECT COUNT( cs.student_id ) AS counter FROM course c, course_student cs WHERE c.id = cs.course_id AND c.course_name = 'Introduction to Database Design' SELECT COUNT( cs.student_id ) FROM Course c INNER JOIN course_student cs ON c.id = cs.course_id WHERE c.course_name = 'Introduction to Database Design' and SELECT COUNT( * ) FROM student JOIN grade ON student.f_name = "Andreas" AND student.l_name = "Pedersen" AND student.id = grade.student_id I know the notation can be a bit hard to paste into HTML forum, but maybe just use some common name or the Greek name. Thanks in advance Mestika

    Read the article

  • Working with Temporal Data in SQL Server

    - by Dejan Sarka
    My third Pluralsight course, Working with Temporal Data in SQL Server, is published. I am really proud on the second part of the course, where I discuss optimization of temporal queries. This was a nearly impossible task for decades. First solutions appeared only lately. I present all together six solutions (and one more that is not a solution), and I invented four of them. http://pluralsight.com/training/Courses/TableOfContents/working-with-temporal-data-sql-server

    Read the article

  • Big Data – Buzz Words: Importance of Relational Database in Big Data World – Day 9 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned what is HDFS. In this article we will take a quick look at the importance of the Relational Database in Big Data world. A Big Question? Here are a few questions I often received since the beginning of the Big Data Series - Does the relational database have no space in the story of the Big Data? Does relational database is no longer relevant as Big Data is evolving? Is relational database not capable to handle Big Data? Is it true that one no longer has to learn about relational data if Big Data is the final destination? Well, every single time when I hear that one person wants to learn about Big Data and is no longer interested in learning about relational database, I find it as a bit far stretched. I am not here to give ambiguous answers of It Depends. I am personally very clear that one who is aspiring to become Big Data Scientist or Big Data Expert they should learn about relational database. NoSQL Movement The reason for the NoSQL Movement in recent time was because of the two important advantages of the NoSQL databases. Performance Flexible Schema In personal experience I have found that when I use NoSQL I have found both of the above listed advantages when I use NoSQL database. There are instances when I found relational database too much restrictive when my data is unstructured as well as they have in the datatype which my Relational Database does not support. It is the same case when I have found that NoSQL solution performing much better than relational databases. I must say that I am a big fan of NoSQL solutions in the recent times but I have also seen occasions and situations where relational database is still perfect fit even though the database is growing increasingly as well have all the symptoms of the big data. Situations in Relational Database Outperforms Adhoc reporting is the one of the most common scenarios where NoSQL is does not have optimal solution. For example reporting queries often needs to aggregate based on the columns which are not indexed as well are built while the report is running, in this kind of scenario NoSQL databases (document database stores, distributed key value stores) database often does not perform well. In the case of the ad-hoc reporting I have often found it is much easier to work with relational databases. SQL is the most popular computer language of all the time. I have been using it for almost over 10 years and I feel that I will be using it for a long time in future. There are plenty of the tools, connectors and awareness of the SQL language in the industry. Pretty much every programming language has a written drivers for the SQL language and most of the developers have learned this language during their school/college time. In many cases, writing query based on SQL is much easier than writing queries in NoSQL supported languages. I believe this is the current situation but in the future this situation can reverse when No SQL query languages are equally popular. ACID (Atomicity Consistency Isolation Durability) – Not all the NoSQL solutions offers ACID compliant language. There are always situations (for example banking transactions, eCommerce shopping carts etc.) where if there is no ACID the operations can be invalid as well database integrity can be at risk. Even though the data volume indeed qualify as a Big Data there are always operations in the application which absolutely needs ACID compliance matured language. The Mixed Bag I have often heard argument that all the big social media sites now a days have moved away from Relational Database. Actually this is not entirely true. While researching about Big Data and Relational Database, I have found that many of the popular social media sites uses Big Data solutions along with Relational Database. Many are using relational databases to deliver the results to end user on the run time and many still uses a relational database as their major backbone. Here are a few examples: Facebook uses MySQL to display the timeline. (Reference Link) Twitter uses MySQL. (Reference Link) Tumblr uses Sharded MySQL (Reference Link) Wikipedia uses MySQL for data storage. (Reference Link) There are many for prominent organizations which are running large scale applications uses relational database along with various Big Data frameworks to satisfy their various business needs. Summary I believe that RDBMS is like a vanilla ice cream. Everybody loves it and everybody has it. NoSQL and other solutions are like chocolate ice cream or custom ice cream – there is a huge base which loves them and wants them but not every ice cream maker can make it just right  for everyone’s taste. No matter how fancy an ice cream store is there is always plain vanilla ice cream available there. Just like the same, there are always cases and situations in the Big Data’s story where traditional relational database is the part of the whole story. In the real world scenarios there will be always the case when there will be need of the relational database concepts and its ideology. It is extremely important to accept relational database as one of the key components of the Big Data instead of treating it as a substandard technology. Ray of Hope – NewSQL In this module we discussed that there are places where we need ACID compliance from our Big Data application and NoSQL will not support that out of box. There is a new termed coined for the application/tool which supports most of the properties of the traditional RDBMS and supports Big Data infrastructure – NewSQL. Tomorrow In tomorrow’s blog post we will discuss about NewSQL. 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

    Read the article

  • Is it easy to switch from relational to non-relational databases with Rails?

    - by Tam
    Good day, I have been using Rails/Mysql for the past while but I have been hearing about Cassandra, MongoDB, CouchDB and other document-store DB/Non-relational databases. I'm planning to explore them later as they might be better alternative for scalability. I'm planning to start an application soon. Will it make a different with Rails design if I move from relational to non-relational database? I know Rails migrations are database-agnostic but wasn't sure if moving to non-relational will make difference with design or not.

    Read the article

  • Is there really Object-relational impedance mismatch?

    - by user52763
    It is always stated that it is hard to store applications objects in relational databases - the object-relational impedance mismatch - and that is why Document databases are better. However, is there really an impedance mismatch? And object has a key (albeit it may be hidden away by the runtime as a pointer to memory), a set of values, and foreign keys to other objects. Objects are as much made up of tables as it is a document. Neither really fit. I can see a use for databases to model the data into specific shapes for scenarios in the application - e.g. to speed up database lookup and avoid joins, etc., but won't it be better to keep the data as normalized as possible at the core, and transform as required?

    Read the article

  • Synonym for "Many-to-Many" relationship (relational databases)

    - by Byron
    What's a synonym for a "many-to-many" relationship? I've finished writing an object-relational mapper but I'm still stumped as to what to name the function that adds that relation. addParent() and addChild() seemed quite logical for the many-to-one/one-to-many and addSuperclass() for one-to-one inheritance, but addManyToMany() would sound quite unintuitive to an object-oriented programmer. addSibling() or addCousin() doesn't really make sense either. Any suggestions? And before you dismiss this as a non-programming question, please remember that consistent naming schemes and encapsulation are pretty integral to programming :)

    Read the article

  • Relational vs. Dimensional Databases, what's the difference?

    - by grautur
    I'm trying to learn about OLAP and data warehousing, and I'm confused about the difference between relational and dimensional modeling. Is dimensional modeling basically relational modeling, but allowing for redundant/un-normalized data? For example, let's say I have historical sales data on (product, city, # sales). I understand that the following would be a relational point-of-view: Product | City | # Sales Apples, San Francisco, 400 Apples, Boston, 700 Apples, Seattle, 600 Oranges, San Francisco, 550 Oranges, Boston, 500 Oranges, Seattle, 600 While the following is a more dimensional point-of-view: Product | San Francisco | Boston | Seattle Apples, 400, 700, 600 Oranges, 550, 500, 600 But it seems like both points of view would nonetheless be implemented in an identical star schema: Fact table: Product ID, Region ID, # Sales Product dimension: Product ID, Product Name City dimension: City ID, City Name And it's not until you start adding some additional details to each dimension that the differences start popping up. For instance, if you wanted to track regions as well, a relational database would tend to have a separate region table, in order to keep everything normalized: City dimension: City ID, City Name, Region ID Region dimension: Region ID, Region Name, Region Manager, # Regional Stores While a dimensional database would allow for denormalization to keep the region data inside the city dimension, in order to make it easier to slice the data: City dimension: City ID, City Name, Region Name, Region Manager, # Regional Stores Is this correct?

    Read the article

  • Haskell Linear Algebra Matrix Library for Arbitrary Element Types

    - by Johannes Weiß
    I'm looking for a Haskell linear algebra library that has the following features: Matrix multiplication Matrix addition Matrix transposition Rank calculation Matrix inversion is a plus and has the following properties: arbitrary element (scalar) types (in particular element types that are not Storable instances). My elements are an instance of Num, additionally the multiplicative inverse can be calculated. The elements mathematically form a finite field (??2256). That should be enough to implement the features mentioned above. arbitrary matrix sizes (I'll probably need something like 100x100, but the matrix sizes will depend on the user's input so it should not be limited by anything else but the memory or the computational power available) as fast as possible, but I'm aware that a library for arbitrary elements will probably not perform like a C/Fortran library that does the work (interfaced via FFI) because of the indirection of arbitrary (non Int, Double or similar) types. At least one pointer gets dereferenced when an element is touched (written in Haskell, this is not a real requirement for me, but since my elements are no Storable instances the library has to be written in Haskell) I already tried very hard and evaluated everything that looked promising (most of the libraries on Hackage directly state that they wont work for me). In particular I wrote test code using: hmatrix, assumes Storable elements Vec, but the documentation states: Low Dimension : Although the dimensionality is limited only by what GHC will handle, the library is meant for 2,3 and 4 dimensions. For general linear algebra, check out the excellent hmatrix library and blas bindings I looked into the code and the documentation of many more libraries but nothing seems to suit my needs :-(. Update Since there seems to be nothing, I started a project on GitHub which aims to develop such a library. The current state is very minimalistic, not optimized for speed at all and only the most basic functions have tests and therefore should work. But should you be interested in using or helping out developing it: Contact me (you'll find my mail address on my web site) or send pull requests.

    Read the article

  • JavaScript computer algebra system

    - by Jonas
    I am looking for a simple computer algebra system (cas) for JavaScript but I can't find anything with google. I only need basic functionality: simplify expressions to some canonic form. Ability to check if two expressions are the same, i.e., a(x+y) == ax+ay parse mathematical formulas. I want it to be able to read expressions like ax²+4x. solve simple equations etc. Do you know of such a library?

    Read the article

  • Converting a certain SQL query into relational algebra

    - by Fumler
    Just doing an assignment for my database course and I just want to double check that I've correctly wrapped my head around relational algebra. The SQL query: SELECT dato, SUM(pris*antall) AS total FROM produkt, ordre WHERE ordre.varenr = produkt.varenr GROUP BY dato HAVING total >= 10000 The relational algebra: stotal >= 10000( ?R(dato, total)( sordre.varenr = produkt.varenr( datoISUM(pris*antall(produkt x ordre)))) Is this the correct way of doing it?

    Read the article

  • Relational algebra help?!

    - by Tom
    im new to relational algebra and finding it difficult. Ive answered a few questions, however they where relatively simple. Could do with help with these though. Database Patient (PatientCode, PatientSurname, PatientFirstname, PatientSex, PatientAge, PatientOccupation, PatientHeight, PatientWeight, PatientAddress) Doctor (DoctorCode, DoctorSurName, DoctorFirstName, DoctorPrivateAddress, MobileNo, Doctor Specilisim) Operation (Operation Code, PatientCode, DoctorCode, Date, Time, Result, OperationType) Is_Seen_By (PatientCode, DoctorCode, Date, Time). Q1. Find the surname and gender of the patients that have been operated on by doctor "DR333" and results have not been successful. Q2. Find the code of the operations that have been done on the 18th of November 2010 and have been successful, please also list the name of the doctors which were involved with the operation.

    Read the article

  • Relational Database pioneer Chris Date is giving a seminar 13th/14th May Edinburgh on "SQL and Relat

    - by tonyrogerson
    One of the pioneers of the Relational Database, Chris Date is giving a 2 day seminar in Edinburgh (13th and 14th May 2010) based around his new book "SQL and Relational Theory - How to Write Accurate SQL Code" which if you don't already have I'd say is a must buy. When I first saw this and what he will cover I thought, oh yer - this is going to cost the earth, well it doesn't - its £750 for the two days and there are discounts available for multiple bookings, being a member...(read more)

    Read the article

  • I want a trivial example of where MongoDB can scale but a relational database will have trouble

    - by Ryan Weir
    I'm just learning to use MongoDB, and when discussing with other programmers would like a quick example of why NoSQL can be a good choice compared to a traditional RDBMS - however the scenarios I come up with and can find online seem pretty contrived. E.g. a blog with lots of traffic could be represented relationally, but will require some performance tuning and joins across tables (assuming full denormalization is being used). Whereas MongoDB would allow direct retrieval from one collection to the same effect. But the response I'm getting from other programmers is "why not just keep it relational and then add some trivial caching later?" Does anybody have a less contrived example where MongoDB will really shine and a relational db will fall over much quicker? The smaller the project/system the better, because it leaves less room for disagreement. Something along the lines of the complexity of the blog example would be really useful. Thanks.

    Read the article

  • Advanced search engine or server for relational database [closed]

    - by Pawel
    In my current project we are storing big volume of data in relational database. One of the recent key requirements is to enrich application by adding some advanced search capabilities. In the Project, performance is one of the important factors due to very large tables (10+ milions of records) with parent-children relations (for example: multi-level parent-child relationship, where I am looking for all parents with specific children). The search engine should also be able to check these references for hits. I have found some potential engines on stack overflow, however it looks like that all of them are dedicated rather for text search than relational db and hosted on linux os: lucene Solr Sphinx As I understand some of them use documents as a source of searching, but is it possible or efficient to create programmaticaly documents based on my relational data? As I am not familiar with all of their features/capabilities can anyone please make some recommendations or propose some different solution? To summarize my requirements: framework/engine to search relational database including decendants. support for Microsoft SQL Server can be used in .NET applications preferably hosted on Windows systems Does any of mentioned above are able to solve my problem? do you know any better solution?

    Read the article

  • Boolean algebra simplification

    - by xbonez
    I need to reduce this boolean expression to its simplest form. Its given that the simplest form contains 3 terms and 7 literals. The expression is: x'yz + w'x'z + x'y + wxy + w'y'z We tried this in class, and even out recitation teacher could not figure it out. Any help would be appreciated.

    Read the article

  • Unexpected result in C algebra for search algorithm.

    - by Rhys
    Hi, I've implemented this search algorithm for an ordered array of integers. It works fine for the first data set I feed it (500 integers), but fails on longer searches. However, all of the sets work perfectly with the other four search algorithms I've implemented for the assignment. This is the function that returns a seg fault on line 178 (due to an unexpected negative m value). Any help would be greatly appreciated. CODE: 155 /* perform Algortihm 'InterPolationSearch' on the set 156 * and if 'key' is found in the set return it's index 157 * otherwise return -1 */ 158 int 159 interpolation_search(int *set, int len, int key) 160 { 161 int l = 0; 162 int r = len - 1; 163 int m; 164 165 while (set[l] < key && set[r] >= key) 166 { 167 168 printf ("m = l + ((key - set[l]) * (r - l)) / (set[r] - set[l])\n"); 169 170 printf ("m = %d + ((%d - %d) * (%d - %d)) / (%d - %d);\n", l, key, set[l], r, l, set[r], set[l]); 171 m = l + ((key - set[l]) * (r - l)) / (set[r] - set[l]); 172 printf ("m = %d\n", m); 173 174 #ifdef COUNT_COMPARES 175 g_compares++; 176 #endif 177 178 if (set[m] < key) 179 l = m + 1; 180 else if (set[m] > key) 181 r = m - 1; 182 else 183 return m; 184 } 185 186 if (set[l] == key) 187 return l; 188 else 189 return -1; 190 } OUTPUT: m = l + ((key - set[l]) * (r - l)) / (set[r] - set[l]) m = 0 + ((68816 - 0) * (100000 - 0)) / (114836 - 0); m = -14876 Thankyou! Rhys

    Read the article

  • relational databases and multicast messages

    - by xRobot
    I have read that relational databases are a terrible way to do multicast messages like twitter. So twitter saves every tweet only one times and then retrieve its in every stream ? or saves every tweet in every users's stream ? I want to know why relational database ( like mysql or postgresql ) doesn't good for twitter-like application.

    Read the article

  • relational data from xml

    - by Beta033
    Our problem is this, we have a relational database to store objects in tables. As any relational database could, several of these tables have multiple foreign keys pointing to other tables (all pretty normal stuff) We've been trying to identify a solution to allow export of this relational data, ideally, only 1 of the objects in the model, to some sort of file (xml, text, ??). So it wouldn't be simple enough to just export 1 table as data stored in other tables would contribute to the complete model of the object. Something like the following picture: Toward this, i've written a routine to export the structure by following the foreign key paths which exports something similar to the following. <Tables> <TableA PK="1", val1, val2, val3> <TableC PK="1", FK_A="1", Val1, val2, val3> <TableC PK="2", FK_A="1", val1, val2, val3> <TableB PK="1", FK_A="1", FK_C="1", val1, val2, val3> <TableB PK="2", FK_A="1", FK_C="2", val1, val2, val3> <TableD PK="1", FK_B="1", FK_C="1", val1> <TableD PK="2", FK_B="2", FK_C="1", val1> </Tables> However, given this structure, it cannot be placed into a heirarchial format (ie D2 is a child of C1 and B2; and B2 is a child of C2) Which in turn, makes my life very difficult when trying to identify a methodology to reimport (and reKey) these objects. Has anybody done anything like this? how do you do it? are there tools or documentation on how this is best accomplished? Thanks for your help.

    Read the article

  • What relational database innovations have there been in the last 10 years

    - by Simon Munro
    The SQL implementation of relational databases has been around in their current form for something like 25 years (since System R and Ingres). Even the main (loosely adhered to) standard is ANSI-92 (although there were later updates) is a good 15 years old. What innovations can you think of with SQL based databases in the last ten years or so. I am specifically excluding OLAP, Columnar and other non-relational (or at least non SQL) innovations. I also want to exclude 'application server' type features and bundling (like reporting tools) Although the basic approach has remained fairly static, I can think of: Availability Ability to handle larger sets of data Ease of maintenance and configuration Support for more advanced data types (blob, xml, unicode etc) Any others that you can think of?

    Read the article

1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >