SQL Functions

PostgreSQL includes several functions that return values based on expressions supplied in the current SQL statement. Moreover, these functions are not constrained to acting on specific data types; rather, they act as control structures within a SQL statement.

CASE WHEN

Description

The CASE WHEN function is a simple conditional evaluation tool. Most programming languages contain similar constructs. It can be thought of as analogous to the ubiquitous IF…THEN…ELSE statement.

Inputs
CASE WHEN condition THEN result 
      [ WHEN condition THEN result ] 
     … 
      [ ELSE result ] 
END
Example

This example shows a classic IF…THEN…ELSE paradigm in which the CASE WHEN function can be used. The age of an employee is compared against certain constants, ...

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