GROUP BY
和 HAVING
子句来查询表中重复的字段。假设你有一个名为 users
的表,并且你想查找 email
字段中的重复值,可以使用以下 SQL 语句:,,``sql,SELECT email, COUNT(*) as count,FROM users,GROUP BY email,HAVING count > 1;,
`,,这个查询会返回所有重复的
email` 以及它们出现的次数。sql,INSERT INTO table_name (column1, column2),SELECT a.column1, b.column2,FROM table_name a,JOIN table_name b ON a.id = b.id,WHERE some_condition;,
`,,这段SQL语句将表
table_name 自身进行关联,并根据条件
some_condition` 将符合条件的数据插入到表中。Powered By Z-BlogPHP 1.7.3
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