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HomeDatabaseMysql Tutorialsql sum() 求和函数的用法

SUM函数返回的一个表达式总的值,这个函数也是非常有用的,下面我们来看看这个函数用详细用法吧

SUM函数的语法是:

 代码如下 复制代码

SELECT SUM(expression )
FROM tables
WHERE predicates;

表达式可以是一个数值字段或公式。

简单的例子

例如,你可能想知道合并全体员工的薪金总额美元以上,其薪酬是25,000/年

 代码如下 复制代码

SELECT SUM(salary) as "Total Salary"
FROM employees
WHERE salary > 25000;

与Example using DISTINCT一起用

 代码如下 复制代码

SELECT SUM(DISTINCT salary) as "Total Salary"
FROM employees
WHERE salary > 25000;

使用公式的示例

在SUM函数中的表达并不需要一个单一的领域。您也可以使用一个公式。例如,您可能需要为业务的净收入。总收入减去总支出纯收入计算。

 代码如下 复制代码

SELECT SUM(income - expenses) as "Net Income"
FROM gl_transactions;


您可能还需要在SUM函数执行数学运算。例如,您可能会确定佣金总额为销售总额的10%。

 代码如下 复制代码

SELECT SUM(sales * 0.10) as "Commission"
FROM order_details;


与Example using GROUP BY

在某些情况下,你将被要求使用SUM函数的第一个集团。

例如,您还可以使用SUM函数返回的部门名称和总销售额(相关部门)。

 代码如下 复制代码

SELECT department, SUM(sales) as "Total sales"
FROM order_details
GROUP BY department;

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