[PostgreSQL] NULLIF

NULLIF(exp1, exp2)

- exp1값과 exp2값이 동일하면 NULL을 그렇지 않으면 exp1을 반환
- CASE WHEN expr1 = expr2 THEN NULL ELSE expr1 END

 

Test

select count(1) from customers; --10

select count(NULLIF(postalcode, '')) as cnt
from customers; --10

select count(NULLIF(postalcode, '12209')) as cnt
from customers; --9

select count(
	case when postalcode = '' then null 
	else postalcode 
	end
	) as cnt 
from customers; --10

select count(
	case when postalcode = '12209' then null 
	else postalcode 
	end
	) as cnt 
from customers; --9

 

테이블정보는 아래 글 참고

https://jieun0113.tistory.com/127

[PostgreSQL] Table Data를 JSON타입으로 만들기

 

Reference

http://www.gurubee.net/lecture/1880

NVL, NVL2, NULLIF, COALESCE