计算 MySQL 表中涉及 ENUM 类型的项目?
mysqlmysqli database更新于 2025/9/4 1:48:17
您可以将 GROUP BY 与聚合函数 COUNT() 一起使用。让我们首先创建一个表 −
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)
以下是使用 ENUM 字段对表中的项目进行计数的查询 −
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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