CASE operator #

CASE [expr] [WHEN expr THEN expr]
            ...
            [ELSE expr]
END

CASE construct implements a basic condition operator. It has two forms:

• CASE with expression

  CASE returns the result of the THEN clause if the result of its expression matches the result of the first WHEN clause.

• CASE without expression

  CASE returns the result of the THEN clause if its corresponding WHEN clause evaluates to true.

For both cases, if no matches are found, the result of the ELSE clause will be returned or NULL if the ELSE clause is not defined. All expression types must match.

-- case expr with else
select
	case 0
		when 1 then 1
		when 2 then 2
		else 3
	end;
[3]

-- case expr
select
	case 0
		when 1 then 1
		when 2 then 2
	end;
[null]

-- case without expr
select
	case
		when id = 2 then 'found'
		else 'not found'
	end
from test;
["not found", "found", "not found"]