在下面的SQL查询中，（2）是什么意思

有人请解释为什么在下面的查询中使用2

select * from employee e 
where(2) = (select count(distinct(e1.sal))
            from employee e1
            where e.sal > e1.sal);

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该查询返回其工资高于其他两个工资的所有员工。括号有误导性，不需要

select * from employee e 
where 2 = (select count(distinct(e1.sal))
            from employee e1
            where e.sal > e1.sal);

例如，给定以下员工数据：

Employee Salary Joe $80,000 Kate $80,000 Lee $85,000 Chris $85,000 Matt $85,000 Mike $90,000 June $90,000 Jack $100,000

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如前所述，数字2周围的括号是无用的。等价的查询可以是

SELECT * FROM 
(
  select sal, DENSE_RANK() OVER (ORDER BY sal) dr from employee
) emp
WHERE emp.dr = 3

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正如您在示例中所看到的，您正在搜索员工表中存在两个不同的较低工资的员工。

意味着您希望通过关联查询从整个员工中获得两个不同的工资。通常情况下，条件写为其中一些条件=5，但是你也可以反过来写：WHERE 5=某个条件。与WHERE select相同…=2 2括号中的2是无用的。因此，在本例中，您选择的是最低工资中第三个的人，即有两个其他员工的工资值低于他/她的工资值。我应该说是员工，而不是个人，因为可能有多个员工 Mike $90,000 June $90,000

  because 90,000 is greater than 80,000 and 85,000

 Notice that Jack is not returned because his salary is greater than 3 other salaries.  Also note there are 5 employees with a salary less than Mike's and June's but the distinct keyword forces the count to 2.

SELECT * FROM 
(
  select sal, DENSE_RANK() OVER (ORDER BY sal) dr from employee
) emp
WHERE emp.dr = 3