本文為英文版的機器翻譯版本,如內容有任何歧義或不一致之處,概以英文版為準。
EXCEPT 查詢範例
資料庫中的CATEGORY資料表包含下列 11 列:
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)
假設 CATEGORY_STAGE 資料表 (預備資料表) 包含額外的一列:
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)
傳回兩個資料表之間的差異。換句話說,傳回位於 CATEGORY_STAGE 資料表但不位於CATEGORY資料表中的資料列:
select * from category_stage except select * from category; catid | catgroup | catname | catdesc -------+----------+---------+---------------------------------- 12 | Concerts | Comedy | All stand up comedy performances (1 row)
下列對等查詢使用同義詞 MINUS。
select * from category_stage minus select * from category; catid | catgroup | catname | catdesc -------+----------+---------+---------------------------------- 12 | Concerts | Comedy | All stand up comedy performances (1 row)
如果您反轉SELECT表達式的順序,查詢不會傳回任何資料列。