As you start coding in SQL, you will use some statements and techniques over and over again. We call these “SQL patterns”. This series will look at the most common SQL patterns and consider how to use them. Previously, we looked at the SQL pattern of matching NULLs. This is important when you are comparing columns containing NULL values. Today, we’re going to consider another SQL practice: conditional summarization with CASE operator.
What happens when you combine CASE with SQL’s data modifying statements? Find out in this article. The CASE expression is a very useful part of SQL and one that you’ll employ frequently. We’ve already covered what the CASE expression does, how to format it, and how to use it in a SELECT statement in “Using CASE to Add Logic to a SELECT”. Another article, “How to Sort Records with the ORDER BY Clause” demonstrated how to use CASE in an ORDER BY clause.
As you write an SQL query, you may need to get values from multiple columns and change values from one form to another. The simple way to achieve this goal is to add a CASE expression to your SELECT statement. In this article, we’ll introduce you to the syntax, formats, and uses of the CASE expression. The CASE expression is a conditional expression: it evaluates data and returns a result.