In SQL Server, the IIF function returns an expression based on the condition. In PostreSQL, you can use the CASE expression.
SQL Server:
-- If condition is true return the first expression, otherwise return the second expression SELECT IIF(2 > 1, 'Yes', 'No') # Yes
PostgreSQL:
-- If condition is true return the first expression, otherwise return the second expression SELECT CASE WHEN 2 > 1 THEN 'Yes' ELSE 'No' END # Yes
For more information, see SQL Server to PostgreSQL Migration.