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1. Definitions
Average values or expression is non-empty and the number of rows in the divided group.
2, Grammar
AVG function syntax is as follows:
AVG( [DISTINCT | ALL] expr )
This syntax can be broken down into the following form:
- AVG (DISTINCT expr)
different values of expr summed and divided by the number of unique occurrence. - AVG (ALL expr)
a non-null value expr each row is added, the number of non-blank lines and obtained by dividing the groups. - AVG (expr)
and AVG (ALL expr) equivalent.
Note: The
data type of the parameter expr must be a NUMBER.
3, Code
/*
作者：AT阿宝哥
日期：2016年9月18日
愿景：参考官方资料，做最好的课程，成就更多职业人！
邮箱：[email protected]
CSDN：https://blog.csdn.net/goldentec
简书：https://www.jianshu.com/u/8a6075d7a2e0
说明：
注意：
*/
-------------------------------------------------------------------------------
--Sample1:原封不动的返回字面量.
SELECT avg(2) FROM emp;
SELECT avg(3) FROM emp;
-------------------------------------------------------------------------------
--Sample2:
select sum(sal)/count(sal) from emp;
select avg(sal) from emp;
-------------------------------------------------------------------------------
--Sample3:
SELECT sum(DISTINCT sal)/count(DISTINCT sal) FROM emp;
SELECT avg(DISTINCT sal) FROM emp;
-------------------------------------------------------------------------------
--Sample4:
SELECT avg(comm) FROM emp;
-------------------------------------------------------------------------------
