The SUM function returns the total sum of a column in a given selection. NULL values are not included in the calculation.
使用SUM函数可以返回给定的选择中列的所有记录值的累计合。NULL值不包括在内。

语法

SELECT SUM(column) FROM table

举例

This example returns the sum of all ages in the "person" table:
这个例子要把在"Persons"表中的所有ages的值累计返回出来:

SELECT SUM(Age) FROM Persons

结果:

98

举例

This example returns the sum of ages for persons that are more than 20 years old:
这个例子会把大于20岁人士的年纪再进行累计计算，并将值返回出来:

SELECT SUM(Age) FROM Persons WHERE Age>20

结果:

79

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