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• Update on T-SQL MERGE

  The MERGE syntax I used here has changed. In 2008 RC0 the "WHEN SOURCE NOT MATCHED" clause is replaced with "WHEN NOT MATCHED BY SOURCE" which is supposed to make the meaning clearer. Although MERGE is part of standard SQL 2003 it's worth noting that Read More... Posted 09 June 2008 18:21 by David.Portas | 0 Comments Filed under: SQL, SQL Server, Katmai, SQL Server 2008

• Not the model, Bill

  According to InfoWorld , Bill Gates thinks that declarative modelling of business logic has not caught on because of "weak models". This is a surprise. E.F.Codd's earliest papers on the Relational Model described a relational calculus for Read More... Posted 12 February 2008 22:27 by David.Portas | 1 Comments Filed under: SQL, Data, Data Modelling

• SQL Server 2008 MERGE

  MERGE is a new DML statement in SQL Server 2008. Microsoft have implemented the ISO SQL 2003 and 2007 standard MERGE statement (as seen in Oracle and DB2) and added some extensions of their own. In a nutshell, MERGE allows you to perform simultaneous Read More... Posted 14 November 2007 21:52 by David.Portas | 2 Comments Filed under: SQL, SQL Server, Katmai, SQL Server 2008

• Relational database pioneer doesn't quite say technology is obsolete!

  According to Computerworld , Mike Stonebraker says "RDBMSes, are 'long in the tooth' and 'should be considered legacy technology'" . Knowing Stonebraker's work and reputation that seemed like some pretty startling information! Read More... Posted 16 September 2007 21:10 by David.Portas | 0 Comments Filed under: SQL, Data

• A note on Updateable CTEs

  One of my regular gripes about SQL Server concerns the number of Transact SQL features that give nondeterministic results. Unfortunately SQL Server 2005 added to the list of those. One of the new ones is ROW_NUMBER(), which is strictly due to ANSI/ISO Read More... Posted 26 July 2007 21:47 by David.Portas | 2 Comments Filed under: SQL, SQL Server

• Relational Futures

  Alice: What do you mean by practical languages? Riccardo: select from where. Alice: That's it? Vittorio: Well, there are of course lots of bells and whistles. Sergio: But basically, this forms the core of most practical languages. [1] Oracle is celebrating Read More... Posted 23 May 2007 07:49 by David.Portas | 0 Comments Filed under: SQL

• Trouble with CHECK Constraints

  ANSI/ISO SQL defines CHECK constraints very simply as: <check constraint definition> ::= CHECK <left paren> <search condition> <right paren> where <search condition> is a boolean expression, including query expressions. In Read More... Posted 19 February 2007 18:36 by David.Portas | 3 Comments Filed under: SQL, SQL Server

• More on Disjoint Subtypes

  My post on Disjoint Subtypes generated some interesting feedback. I made a point of saying that the Products table in my schema is in BCNF. That’s because the only determinants are supersets of {SKU}, which is the only key. The point I wanted to Read More... Posted 19 February 2007 13:24 by David.Portas | 0 Comments Filed under: SQL, Data Modelling

• Distributed Keys and Disjoint Subtypes

  Entity subtyping is a very common data modelling scenario that gets extensive coverage in books on relational design but it isn’t necessarily well supported by SQL DBMSs. The following is a simple technique I have found useful for implementing some Read More... Posted 08 January 2007 22:35 by David.Portas | 5 Comments Filed under: SQL, Data Modelling