Database Fundamentals #24: More Filtering Data

In this post, we continue discussing the functionality of the WHERE clause. We started with the basics of the logic using things like AND, OR, and LIKE or ‘=’. Now, we’ll expand into some other areas.

Functions in the WHERE Clause

SQL Server provides you with all sorts of functions that can be used to manipulate strings, modify dates or times or perform arcane mathematical equations. The problem with these is that if you do them on columns in tables it can lead to performance issues. The trick then, is to not perform functions on the columns in the tables. We’ll cover this in more detail when we get to indexing, variables, and parameters. Just don’t get into the habit of putting functions on the columns in your tables in the WHERE clause.

Source de l’article sur DZONE