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仅显示在MySQL中出现至少三次的重复列名

2024-05-16 07:31:07 512

COUNT()为此使用HAVING。让我们首先创建一个表-

mysql> create table DemoTable1351
    -> (
    -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
    -> StudentName varchar(40)
    -> );

使用插入命令在表中插入一些记录-

mysql> insert into DemoTable1351(StudentName) values('Chris');
mysql> insert into DemoTable1351(StudentName) values('Bob');
mysql> insert into DemoTable1351(StudentName) values('Bob');
mysql> insert into DemoTable1351(StudentName) values('David');
mysql> insert into DemoTable1351(StudentName) values('Bob');
mysql> insert into DemoTable1351(StudentName) values('David');
mysql> insert into DemoTable1351(StudentName) values('Bob');
mysql> insert into DemoTable1351(StudentName) values('Mike');
mysql> insert into DemoTable1351(StudentName) values('David');

使用select语句显示表中的所有记录-

mysql> select * from DemoTable1351;

这将产生以下输出-

+-----------+-------------+
| StudentId | StudentName |
+-----------+-------------+
|         1 | Chris       |
|         2 | Bob         |
|         3 | Bob         |
|         4 | David       |
|         5 | Bob         |
|         6 | David       |
|         7 | Bob         |
|         8 | Mike        |
|         9 | David       |
+-----------+-------------+
9 rows in set (0.00 sec)

这是显示至少出现三次的重复列名的查询-

mysql> select * from DemoTable1351
    -> group by StudentName
    -> having count(StudentName) >=3;

这将产生以下输出-

+-----------+-------------+
| StudentId | StudentName |
+-----------+-------------+
|         2 | Bob         |
|         4 | David       |
+-----------+-------------+
2 rows in set (0.00 sec)

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仅显示在MySQL中出现至少三次的重复列名

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