从 MySQL 中单个列中获取重复值的计数？

让我们首先创建一个表 -

mysql> create table DemoTable
   -> (
   -> Number int
   -> );
Query OK, 0 rows affected (0.83 sec)

使用 insert 命令在表中插入一些记录 -

mysql> insert into DemoTable values(20);
Query OK, 1 row affected (0.23 sec)

mysql> insert into DemoTable values(20);
Query OK, 1 row affected (0.14 sec)

mysql> insert into DemoTable values(10);
Query OK, 1 row affected (0.23 sec)

mysql> insert into DemoTable values(30);
Query OK, 1 row affected (0.14 sec)

mysql> insert into DemoTable values(10);
Query OK, 1 row affected (0.47 sec)

mysql> insert into DemoTable values(10);
Query OK, 1 row affected (0.15 sec)

使用 select 语句显示表中的所有记录 -

mysql> select *from DemoTable;

这会产生以下输出 -

+--------+
| Number |
+--------+
|     20 |
|     20 |
|     10 |
|     30 |
|     10 |
|     10 |
+--------+
6 rows in set (0.00 sec)

以下是查询从单个列中选择 count 值 -

mysql> select Number,count(*) from DemoTable group by Number;

这会产生以下输出 -

+--------+----------+
| Number | count(*) |
+--------+----------+
|     20 |        2 |
|     10 |        3 |
|     30 |        1 |
+--------+----------+
3 rows in set (0.00 sec)

莎伦·克里斯汀

更新日期：30-Jul-2019

173 次访问

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