資料表：

sql程式碼：

delete  FROM  test where id NOT in(  select id FROM tmp  )


create table tmp (select id FROM test GROUP BY `name` )

tmp是建立的臨時表，不需要提前建立，直接寫接好，

為什麼要建立臨時表，看下面：

直接寫會報錯 ：  

delete  FROM  test where id NOT in(  select id FROM test GROUP BY `name`  )

[SQL]

delete  FROM  test where id NOT in(  select id FROM test GROUP BY `name`  )

[Err] 1093 - You can't specify target table 'test' for update in FROM clause

要先執行create table tmp (select id FROM test GROUP BY `name` ) 

先建立臨時表，才能查詢