如果基于另一列在1列中重复，则删除

Question

我试图从ID重复的表中删除数据但是将另一列保留在某个值

key .   id .    info .    flag
1 .     A .     apple .   y
2 .     B .     banana .  n
3 .     B .     banana .  y
4 .     C .     orange .  n

我想删除第2行＆＃34; id＆＃34;是重复的并保持标志值为＆＃34; y＆＃34;。该表是> 100K行

我尝试过DISTINCT和GROUP BY的各种组合而没有很好的结果

Answer 1

您可以使用group by，count和having来过滤可能的id 如果你想用y

删除值

  delete from 
  my_table where id in (
     select t.id from(
      select id
      from my_table 
      group by id
      having count(*) > 1
  )  t 
  and flag ='y') 

否则如果你想保留y那么

  delete from 
  my_table where id in (
     select t.id from(
      select id
      from my_table 
      group by id
      having count(*) > 1
  )  t 
  and flag <>'y')