mysql中这样写GROUP BY和count居然不会出错？

╰+哭是因爲堅強的太久メ 2023-02-23 07:43 13阅读 0赞

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SELECT * FROM salary;
    SELECT deptId, MAX(sal) FROM salary;
    SELECT empId, deptId, MAX(sal) FROM salary;
    SELECT deptId, MAX(sal), AVG(sal) , MIN(sal) FROM salary GROUP BY deptId;
    SELECT empId, deptId, MAX(sal) FROM salary GROUP BY deptId;
    SELECT empId, deptId, MIN(sal) FROM salary GROUP BY deptId;
    SELECT empId, deptId, AVG(sal) FROM salary GROUP BY deptId;
    SELECT empId, deptId, SUM(sal) FROM salary GROUP BY deptId;
    SELECT empId, deptId, COUNT(sal) FROM salary GROUP BY deptId;
    SELECT * FROM salary;
    SELECT
    	COUNT(*),
    	COUNT(1),
    	COUNT(66),
    	COUNT(88),
    	COUNT(empId),
    	COUNT(deptId),
    	COUNT(sal),
    	COUNT('aaa'),
    	COUNT('bbb'),
    	COUNT(0),
    	COUNT(NULL)
    FROM
    	salary;

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