我们可以使用 COUNT(*) 和 GROUP BY 子句来找出列中某个值的重复情况。以下是在“Student”表的“Name”列上使用 COUNT(*) 和 GROUP BY 子句的示例来演示 -
mysql> select count(*),name from student group by name; +----------+---------+ | count(*) | name | +----------+---------+ | 1 | Aarav | | 2 | Gaurav | | 1 | Harshit | +----------+---------+ 3 rows in set (0.00 sec)
上面查询的结果集显示了哪个值在列中重复了多少次。在上面的示例中，“Gaurav”在“name”列中重复两次。可以从下面的‘SELECT *’ 查询中验证同样的情况 -
mysql> Select * from Student; +------+---------+---------+-----------+ | Id | Name | Address | Subject | +------+---------+---------+-----------+ | 1 | Gaurav | Delhi | Computers | | 2 | Aarav | Mumbai | History | | 15 | Harshit | Delhi | Commerce | | 20 | Gaurav | Jaipur | Computers | +------+---------+---------+-----------+ 4 rows in set (0.00 sec)
