MySQL | 聚合函数的使用

Zkeq

发布于 2022-05-18 15:34:56

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文章被收录于专栏：ZkeqZkeq

数据操作语言：聚合函数

SELECT AVG(sal+IFNULL(comm,0)) FROM t_emp;

SELECT AVG(sal+IFNULL(comm,0)) AS avg
FROM t_emp;

SELECT SUM(ename) FROM t_emp;

SELECT SUM(sal) FROM t_emp
WHERE deptno IN (10,20);

SELECT SUM(sal)
FROM t_emp WHERE deptno IN(10,20);

SELECT MAX(comm) FROM t_emp;

SELECT MAX(sal+IFNULL(comm,0)) FROM t_emp
WHERE deptno IN(10,20)

SELECT MAX(LENGTH(ename)) FROM t_emp;

SELECT MIN(empno) FROM t_emp;
SELECT MIN(hiredate) FROM t_emp;

SELECT AVG(sal+IFNULL(comm,0)) FROM t_emp;

SELECT AVG(ename) FROM t_emp;

SELECT COUNT(*) FROM t_emp;

SELECT COUNT(comm) FROM t_emp;

SELECT 
	COUNT(*), COUNT(comm)
FROM t_emp;

SELECT COUNT(*) FROM t_emp
WHERE deptno IN(10,20) AND sal>= 2000
AND DATEDIFF(NOW(), hiredate)/365>=15;

SELECT COUNT(*) FROM t_emp
WHERE hiredate>="1985-01-01"
AND sal>AVG(sal); -- XXXXXXXX
-- 聚合函数永远不能出现在 WHERE 子句里面

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原始发表：2022-04-26，如有侵权请联系 cloudcommunity@tencent.com 删除