EXCEPT 쿼리 예

데이터베이스의 CATEGORY 테이블에는 다음과 같은 11개의 행이 있습니다.

 catid | catgroup |  catname  |                  catdesc
-------+----------+-----------+--------------------------------------------
   1   | Sports   | MLB       | Major League Baseball
   2   | Sports   | NHL       | National Hockey League
   3   | Sports   | NFL       | National Football League
   4   | Sports   | NBA       | National Basketball Association
   5   | Sports   | MLS       | Major League Soccer
   6   | Shows    | Musicals  | Musical theatre
   7   | Shows    | Plays     | All non-musical theatre
   8   | Shows    | Opera     | All opera and light opera
   9   | Concerts | Pop       | All rock and pop music concerts
  10   | Concerts | Jazz      | All jazz singers and bands
  11   | Concerts | Classical | All symphony, concerto, and choir concerts
(11 rows)

CATEGORY_STAGE 테이블(스테이징 테이블)에 추가적인 행이 한 개 있다고 가정합니다.

 catid | catgroup |  catname  |                  catdesc
-------+----------+-----------+--------------------------------------------
   1   | Sports   | MLB       | Major League Baseball
   2   | Sports   | NHL       | National Hockey League
   3   | Sports   | NFL       | National Football League
   4   | Sports   | NBA       | National Basketball Association
   5   | Sports   | MLS       | Major League Soccer
   6   | Shows    | Musicals  | Musical theatre
   7   | Shows    | Plays     | All non-musical theatre
   8   | Shows    | Opera     | All opera and light opera
   9   | Concerts | Pop       | All rock and pop music concerts
  10   | Concerts | Jazz      | All jazz singers and bands
  11   | Concerts | Classical | All symphony, concerto, and choir concerts
  12   | Concerts | Comedy    | All stand up comedy performances
(12 rows)

두 테이블 사이의 차이점을 반환합니다. 다시 말해, CATEGORY_STAGE 테이블에는 있지만 CATEGORY 테이블에는 없는 행을 반환합니다.

select * from category_stage
except
select * from category;

catid | catgroup | catname |             catdesc
-------+----------+---------+----------------------------------
  12  | Concerts | Comedy  | All stand up comedy performances
(1 row)

다음과 같은 동등한 쿼리는 동의어 MINUS를 사용합니다.

select * from category_stage
minus
select * from category;

catid | catgroup | catname |             catdesc
-------+----------+---------+----------------------------------
  12  | Concerts | Comedy  | All stand up comedy performances
(1 row)

SELECT 표현식의 순서를 반대로 하면 쿼리가 아무런 행도 반환하지 않습니다.