php mysql 求和语句

//自动计算二个字段的值赋给另一字段sql

$sql ="update table set sum = mathe +language";

//求一个字段列的数据总和

$sql = "select sum(sum) from tables";

//下们我们来看个实例

/*
创建表
CREATE TABLE `cc`.`sumtable` (
`id` INT( 4 ) NOT NULL ,
`a1` INT( 4 ) NOT NULL ,
`a2` INT( 4 ) NOT NULL ,
`summ` INT( 8 ) NOT NULL
) ENGINE = InnoDB

插入记录

INSERT INTO `cc`.`sumtable` (
`id` ,
`a1` ,
`a2` ,
`summ`
)
VALUES (
'1', '5', '5', '0'
), (
'2', '6', '5', '0'
);
*/

//自动计算二个字段的值赋给另一字段sql
update sumtable set summ = a1+a2

//求和
SELECT sum( summ ) FROM sumtable
sum(summ)
21

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