I’m an outspoken advocate of always using a clustered index on each and every table you create as a matter of best practice. But even I will agree that there’s a case for using the odd heap now and then.
delete
Using DELETE on subqueries and common table expressions
Here’s an interesting feature I found in the code of a colleague the other day. A common task in T-SQL is eliminating duplicate records. This became a lot easier with the introduction of windowed functions way back in SQL Server 2005, such as ROW_NUMBER(), but it turns out, I’ve still been missing out on a really simple and cool solution.
The assert operator and different types of updates
When you update a column that is tied to a foreign key constraint, SQL Server needs to validate (called “assert“) the new value, in order to make sure that you haven’t added a value with no matching primary key. But in some situations, it’ll assert more than just the column(s) you updated.
Cool MERGE features you may not know about
The MERGE statement is a really powerful way to create what’s called “upserts”. In this article, I’ll take a more detailed look at how you can make the best use of MERGE and I’ll also show you some cool tricks I picked up along the way.
Using MERGE to insert, delete and update all-in-one
As of SQL Server 2008, there’s a new powerful consolidation statement in the DML toolbox: MERGE. Using MERGE, you can perform so-called “upserts”, i.e. one statement that performs an insert, delete and/or update in a single statement. And, more importantly, with just a single join.
Using OUTPUT with DML statements
The OUTPUT clause allows you to combine DML statements with a kind of SELECT statement on the rows affected by the DML operation. This is a powerful way to visualize what records were touched by your statement, or an easy way to build an auditing mechanism.
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