在数据库中查找重复的列多个值

Question

我有一个包含以下列的 sqlite 数据库：

id   home   path    name    layer
1   /home   test    user1   1
2   /etc    test2   user2   1
3   /home   test    user3   1
4   /home   test    user4   1
5   /home   test    user1   1
6   /etc    test2   user2   1

如果 home、path 和 name 相等，但前提是所有 3 个都相同，我如何删除所有重复项？

Sl id 1 应该删除，因为它是 id 5 的副本，id 2 应该删除，因为它是 id 6 的副本。

它应该是这样的：

id   home   path    name    layer
3   /home   test    user3   1
4   /home   test    user4   1
5   /home   test    user1   1
6   /etc    test2   user2   1

Answer 1

您可以通过 group by 实现此目的：

select
  *
from data

group by "home", "path", "name"
having max("id")

order by "id"

sqlfiddle

Answer 2

如果您确实想删除重复项，则使用存在逻辑：

DELETE
FROM yourTable
WHERE EXISTS (SELECT 1 FROM yourTable t2
              WHERE t2.home = yourTable.home AND
                    t2.path = yourTable.path AND
                    t2.name = yourTable.name AND
                    t2.id > yourTable.id);

如果您只想查看您的数据，请尝试：

SELECT t1.*
FROM yourTable t1
WHERE NOT EXISTS (SELECT 1 FROM yourTable t2
                  WHERE t2.home = t1.home AND t2.path = t1.path AND
                        t2.name = t1.name AND t2.id > t1.id);

Answer 3

您可以按 home、path、name 和 select MAX(id).
列分组在这种情况下，对于 3 列的每个组合，SQLite 将 return 只有 1 行，即最大 id:

SELECT MAX(id) id, home, path, name, layer
FROM tablename
GROUP BY home, path, name
ORDER BY id

这是一个documented feature of SQLite.

如果要删除重复项：

DELETE FROM tablename
WHERE id NOT IN (SELECT MAX(id) FROM tablename GROUP BY home, path, name)

参见demo。
结果：

id	home	path	name	layer
3	/home	test	user3	1
4	/home	test	user4	1
5	/home	test	user1	1
6	/etc	test2	user2	1

在数据库中查找重复的列多个值

Find duplicate column multiple value in db

sqlite

sql-delete