Question

我的表中有一些行需要根据重复的几列进行删除。

例如Col1，Col2，Col3，Col4

如果Col1，Col2和Col3是重复的，无论Col4中的值是多少，我都希望删除这些重复项。我该怎么做呢？

Answer 1

您可以使用where子句执行此操作：

delete from t
    where (col1, col2, col3) in (select col1, col2, col3
                                 from t
                                 group by col1, col2, col3
                                 having count(*) > 1
                                );

Answer 2

按这些ID分组并检查是否有重复项。这样找到的重复项删除了记录。

delete from mytable 
where  (col1,col2,col3) in
(
  select col1,col2,col3
  from mytable 
  group by col1,col2,col3
  having count(*) > 1
);

Answer 3

如果另一行具有相同的col1，col2和col3并且col4值较低，则使用EXISTS删除行。即保留一个col1，col2，col3行。

delete from tablename t1
where exists (select 1 from tablename t2
              where t2.col1 = t1.col1
                and t2.col2 = t1.col2
                and t2.col3 = t1.col3
                and t2.col4 < t1.col4)

要删除两个/所有行，请跳过col4条件，改为group by：

delete from tablename t1
where exists (select 1 from tablename t2
              where t2.col1 = t1.col1
                and t2.col2 = t1.col2
                and t2.col3 = t1.col3
              group by t2.col1, t2.col2, t2.col3
              having count(*) > 1)

在ORACLE SQL中删除半重复行

3 个答案: