What is the purpose of the case statement in SQL?

The CASE statement in SQL is used for conditional evaluation and branching in a query.

The CASE statement evaluates a given condition and returns the result that meets the condition. It can be used in statements such as SELECT, WHERE, ORDER BY, and HAVING.

There are two forms of CASE statement:

1. Simple CASE expression: making a decision based on the value of a field or expression. For example:

SELECT column_name,
       CASE expression
           WHEN value1 THEN result1
           WHEN value2 THEN result2
           ...
           ELSE result
       END
FROM table_name;

1. Search CASE statement: evaluate based on multiple conditions.
   For example:

SELECT column_name,
       CASE
           WHEN condition1 THEN result1
           WHEN condition2 THEN result2
           ...
           ELSE result
       END
FROM table_name;

The uses of a CASE statement include, but are not limited to:

1. Convert the value of a field into another value or categorize it.
2. Add a new calculated field to the query results.
3. Sort, filter, or group based on different conditions.
4. Use conditional logic in queries to determine and control the execution flow of statements.