使用包含ENUM字段的MySQL表计算项？

您可以使用GROUP BY和聚合函数COUNT()。首先让我们创建一个表 –

mysql> create table DemoTable
   ( 
   Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Size ENUM('S','M','L','XL')
   );
Query OK, 0 rows affected (0.69 sec)

使用insert命令在表中插入一些记录 –

mysql> insert into DemoTable(Size) values('L');
Query OK, 1 row affected (0.19 sec)

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

mysql> insert into DemoTable(Size) values('S');
Query OK, 1 row affected (0.30 sec)

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

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

mysql> insert into DemoTable(Size) values('M');
Query OK, 1 row affected (0.13 sec)

mysql> insert into DemoTable(Size) values('M');
Query OK, 1 row affected (0.10 sec)

mysql> insert into DemoTable(Size) values('M');
Query OK, 1 row affected (0.10 sec)

mysql> insert into DemoTable(Size) values('XL');
Query OK, 1 row affected (0.08 sec)

使用select语句显示表中的所有记录 –

mysql> select *from DemoTable;

这将产生以下输出 –

+----+------+
| Id | Size |
+----+------+
|  1 | L    |
|  2 | S    |
|  3 | S    |
|  4 | M    |
|  5 | XL   |
|  6 | M    |
|  7 | M    |
|  8 | M    |
|  9 | XL   |
+----+------+
9 rows in set (0.00 sec)

下面是查询使用table字段计算表中项的查询 –

mysql> SELECT tbl.Size, COUNT(1) AS Frequency from DemoTable tbl group by tbl.Size;

这将产生以下输出 –

+------+-----------+
| Size | Frequency |
+------+-----------+
| L    |         1 |
| S    |         2 |
| M    |         4 |
| XL   |         2 |
+------+-----------+
4 rows in set (0.00 sec)

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