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如何在MySQL中选择所有重复项？

2024-05-11 13:08:03 459

若要选择重复项，可以使用子查询。让我们首先创建一个表-

mysql> create table DemoTable
   -> (
   -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   -> Name varchar(100)
   -> );

使用插入命令在表中插入一些记录-

mysql> insert into DemoTable(Name) values('John');

mysql> insert into DemoTable(Name) values('Chris');

mysql> insert into DemoTable(Name) values('John');

mysql> insert into DemoTable(Name) values('David');

mysql> insert into DemoTable(Name) values('Bob');

mysql> insert into DemoTable(Name) values('Chris');

mysql> insert into DemoTable(Name) values('Mike');

mysql> insert into DemoTable(Name) values('Robert');

mysql> insert into DemoTable(Name) values('Mike');

使用select语句显示表中的所有记录-

mysql> select *from DemoTable;

输出结果

+----+--------+
| Id | Name   |
+----+--------+
| 1  | John   |
| 2  | Chris  |
| 3  | John   |
| 4  | David  |
| 5  | Bob    |
| 6  | Chris  |
| 7  | Mike   |
| 8  | Robert |
| 9  | Mike   |
+----+--------+
9 rows in set (0.00 sec)

以下是选择所有重复项的查询-

mysql> select *from DemoTable
   -> where Name in (select Name from DemoTable group by Name having count(*) > 1);

输出结果

+----+-------+
| Id | Name  |
+----+-------+
| 1  | John  |
| 2  | Chris |
| 3  | John  |
| 6  | Chris |
| 7  | Mike  |
| 9  | Mike  |
+----+-------+
6 rows in set (0.09 sec)

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如何在MySQL中选择所有重复项？

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