MySQL 如何利用COUNT(*)和GROUP BY语句判断列中值的重复次数？

我们可以利用COUNT()和GROUP BY语句来找出列中值的重复次数。以下是用于在“学生”表格的“Name”列上，展示COUNT()和GROUP BY语句的实例。

mysql> select count(*),name from student group by name;

+----------+---------+
| count(*) | name    |
+----------+---------+
| 1        | Aarav   |
| 2        | Gaurav  |
| 1        | Harshit |
+----------+---------+

3 rows in set (0.00 sec)

上述查询的结果集显示了哪个值在该列中重复出现，以及重复了多少次。在上述实例中，“Gaurav”重复了两次。以下使用 “SELECT *” 查询来验证此结果―

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)

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