SQL查询删除多行

Question

How we can delete multiple rows having columns from a db? Suppose db has following data (id, list_name, user) and list_name has values as:

 Owner-aaa
 coowner-aaa
 owner-aaa
 subowner-aaa

How we can delete the rows having "Owner-aaa" and "owner-aaa" which are duplicates?

Can we add something in this query here:

delete from <table_name> where list_name = 'owner-aaa'

But it deletes only lower case list, I want something general which checks duplicates in small and caps and delete both of them?

Thanks in advance Amy

Answer 1

delete from tableName where LOWER(list_name) = 'owner-aaa'

Answer 2

DELETE FROM mytable WHERE LOWER(listname) IN
(SELECT LOWER(listname) FROM mytable 
GROUP BY LOWER(listname)
HAVING COUNT(*) > 1)

Answer 3

DELETE a
FROM list a
INNER JOIN list b ON LOWER(a.list_name)=LOWER(b.list_name)
WHERE a.id <> b.id

Answer 4

Meaby you can use LOWER/UPPER sql functions.

But are you sure your model is correct? It seem realy weird to have a name list like that. That should be another table NAMES with ID and NAME field. It's a 1-N relation.

Answer 5

I'm not entirely sure from your question whether you want to delete all rows where duplicates occur, or leave one, and remove only the true duplicates. So here's a shot at each:

To remove only the true duplicates:

DELETE FROM MyTable WHERE id IN
(
   SELECT T1.id 
     FROM MyTable T1
          INNER JOIN MyTable T2
             ON UPPER(T1.list_name) = UPPER(T2.list_name)
            AND T2.id <> T1.id
            AND (T1.id <> (SELECT MAX(id) FROM MyTable WHERE UPPER(list_name) = UPPER(T1.list_name))
) DUPS

This presumes that the id field is unique to each record

To remove all records where there are duplicates, remove the two "AND" clauses in the subquery.