Exemplos de consultas EXCEPT

A tabela CATEGORY no banco de dados contém as 11 linhas a seguir:

 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)

Pressuponha que uma tabela CATEGORY_STAGE (tabela de preparação) contém uma linha adicional:

 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)

Retorne a diferença entre as duas tabelas. Em outras palavras, retorne as linhas que estão na tabela CATEGORY_STAGE, mas não na tabela CATEGORY:

select * from category_stage
except
select * from category;

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

A consulta equivalente a seguir usa o sinônimo MINUS.

select * from category_stage
minus
select * from category;

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

Se você reverter a ordem das expressões SELECT, a consulta não retornará qualquer linha.