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如何在MySQL中删除重复项并在表中保留一行？

2024-04-21 02:20:06 343

要删除重复项并在表中保留一行，您需要使用临时表的概念。步骤如下-

create table anytemporaryTableName as select distinct yourColumnName1, yourColumnName2 from yourTableName;
truncate table yourTableName;
insert into yourTableName(yourColumnName1, yourColumnName2) select yourColumnName1, yourColumnName2 from yourtemporaryTableName ;
drop table yourtemporaryTableName ;

让我们创建一个表-

mysql> create table demo39
−> (
−> user_id int,
−> user_name varchar(20)
−> );

借助insert命令将一些记录插入表中-

mysql> insert into demo39 values(10,'John');

mysql> insert into demo39 values(10,'John');

mysql> insert into demo39 values(11,'David');

mysql> insert into demo39 values(11,'David');

使用select语句显示表中的记录-

mysql> select *from demo39;

这将产生以下输出-

+---------+-----------+
| user_id | user_name |
+---------+-----------+
|      10 | John      |
|      10 | John      |
|      11 | David     |
|      11 | David     |
+---------+-----------+
4 rows in set (0.00 sec)

以下是删除重复项并在表中保留一行的查询-

mysql> create table temporaryTable as select distinct user_id, user_name from demo39;
Records: 2 Duplicates: 0 Warnings: 0

mysql> truncate table demo39;

mysql> insert into demo39(user_id, user_name) select user_id, user_name from temporaryTable;
Records: 2 Duplicates: 0 Warnings: 0

mysql> drop table temporaryTable;

使用select语句显示表中的记录-

mysql> select *from demo39;

这将产生以下输出-

+---------+-----------+
| user_id | user_name |
+---------+-----------+
|      10 | John      |
|      11 | David     |
+---------+-----------+
2 rows in set (0.00 sec)

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如何在MySQL中删除重复项并在表中保留一行？

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