Case statement in sql

Problem

The WHERE clause in SQL queries filters data based on a specified expression or condition. We usually define a static condition or value, however, if you need to filter data based on different conditions, this can be done using SQL CASE in the WHERE clause.

Solution

This SQL tutorial will guide you on conditionally filtering using the WHERE clause using a SQL CASE statement.

Introduction to SQL CASE Statement

The SQL CASE statement specifies a conditional expression to perform different actions depending on the input expression value.

The syntax for the CASE statement in a SQL database is:

For example, in the AdventureWorks2019 sample database, look at the [MaritalStatus] column value from the [HumanResources].[Employee] table. It contains the abbreviation “S” for Single and “M” for Married.

We can use a CASE statement to replace the abbreviation with the custom text, as shown below.

It changes the abbreviations “S” and “M” to “Single” and “Married&#

case when in sql query where clause

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