因為系統bug在對所在店鋪的會員進行遮蔽的時候沒有進行查重操作，導致在遮蔽表中出現了重複的資料，所以需要刪除此表中姓名重複的資料，並保留其中的一條。模擬資料如下圖:

第一條sql :

delete from t_black_list where sellerId = 120055122 and names in (
  select names from t_black_list where sellerId = 120055122 and types = 4 group by names having count(names) > 1
)
and id not in (
  select
 
 id from t_black_list where sellerId = 120055122 and types = 4 group by names having count(names) > 1
)

遇到了問題:

遇到You can’t specify target table ‘表名’ for update in FROM clause這樣的錯誤，它的意思是說，不能先select出同一表中的某些值，再update這個表(在同一語句中)，即不能依據某欄位值做判斷再來更新某欄位的值。

解決:(中間表過度)

 select * from t_black_list where
 
 sellerId = 120055122  and names in (
  SELECT a.names from (select names from t_black_list where sellerId = 120055122  and types = 4 group by names having count(names) > 1) a
)
and id not in (
  SELECT b.id  from (select id from t_black_list where sellerId = 120055122  and types = 4 group by names having
 
 count(names) > 1) b
)

注:
mysql group by 會選擇id最小的那個