postgres functions : difference between CASE WHEN and IF ELSE

Question

Can any one let me know what the differences are between WHEN CASE .. and IF/ELSE when writing in Postgres functions.

Answer 1

The problem is which CASE do you mean?

One CASE is an expression. It can appear inside expressions, like A + CASE ... + B. Along with COALESCE, NULLIF, GREATEST and LEAST it makes the group of conditional expressions.

The other CASE, along with IF, is a control structure (a conditional). It can appear in the SQL control flow to chose what blocks/statements are executed, based on a condition.