仅显示 MySQL 中至少出现三次的重复列名
mysqlmysqli database更新于 2024/3/14 22:01:00
为此使用 HAVING COUNT()。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) -> ); Query OK, 0 rows affected (1.08 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable1351(StudentName) values('Chris');
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('David');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('David');
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable1351(StudentName) values('Mike');
Query OK, 1 row affected (0.68 sec)
mysql> insert into DemoTable1351(StudentName) values('David');
Query OK, 1 row affected (0.12 sec)
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)
以下查询用于显示至少出现三次的重复列名 −
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)
