如何在 MySQL 中计算多列的值?
mysqlmysqli database更新于 2023/12/18 20:00:00
要计算多列的值，请使用 GROUP BY。以下是语法 −
select yourColumnName1,sum(yourColumnName2*yourColumnName3) AS anyAliasName from yourTableName group by yourColumnName1;
首先我们创建一个表 −
mysql> create table calculateValueDemo -> ( -> Id int, -> ProductPrice int, -> ProductWeight int -> ); Query OK, 0 rows affected (0.56 sec)
下面是使用 insert 命令向表中插入记录的查询 −
mysql> insert into calculateValueDemo values(100,35,5); Query OK, 1 row affected (0.16 sec) mysql> insert into calculateValueDemo values(101,50,3); Query OK, 1 row affected (0.16 sec) mysql> insert into calculateValueDemo values(100,100,4); Query OK, 1 row affected (0.17 sec) mysql> insert into calculateValueDemo values(101,500,2); Query OK, 1 row affected (0.22 sec)
以下是使用 select 语句显示表中的所有记录的查询 −
mysql> select * from calculateValueDemo;
这将产生以下输出 −
+------+--------------+---------------+ | Id | ProductPrice | ProductWeight | +------+--------------+---------------+ | 100 | 35 | 5 | | 101 | 50 | 3 | | 100 | 100 | 4 | | 101 | 500 | 2 | +------+--------------+---------------+ 4 rows in set (0.00 sec)
这是从多列计算值的查询 −
mysql> select Id,sum(ProductPrice*ProductWeight) AS Total from calculateValueDemo group by Id;
这将产生以下输出 −
+------+-------+ | Id | Total | +------+-------+ | 100 | 575 | | 101 | 1150 | +------+-------+ 2 rows in set (0.00 sec)
