使用计数限制基于连接表的行答案

【问题标题】：Restrict rows based on a join table, using a count使用计数限制基于连接表的行
【发布时间】：2012-06-27 15:28:23
【问题描述】：

我有一个员工表和一个假期表，其中每一行代表他们休假的一天。

我想让所有休假天数超过其最大休假天数的员工。

employees:
employeeId
maxVacationDays

vacations:
employeeId
date_vacation_day_taken

我现在的疑问：

SELECT e.*
FROM employees e
         INNER JOIN vacations v ON (v.employeeId = e.employeeId)
WHERE e.isActive = true AND ( ???? > e.maxVacationDays)

所以我需要从休假表中获取该employeeId 的行数。

我需要一个子查询吗？

（使用sql2000）

【问题讨论】：

标签： sql sql-server sql-server-2000

【解决方案1】：

试试这个：

SELECT e.employeeId, v.maxVacationDays
FROM employees e
         INNER JOIN vacations v ON (v.employeeId = e.employeeId)
WHERE e.isActive = true
GROUP BY e.employeeId, v.maxVacationDays
HAVING COUNT(v.employeeId) > v.maxVacationDays

【讨论】：

【解决方案2】：

试试这个：

SELECT * FROM 
(
    SELECT e.employeeId, e.maxVacationDays, 
           SUM(v.date_vacation_day_taken) 'dayscount'
    FROM employees e
    INNER JOIN vacations v ON (v.employeeId = e.employeeId)
    GROUP BY e.employeeId, e.maxVacationDays
    WHERE e.isactive = true
) sub
WHERE sub.dayscount > e.maxVacationDays)

【讨论】：

【解决方案3】：

也许是这样的：

select e.employeeId, e.maxVacationDays, count(v.*) as vacationDaysTaken
from employees e
    join vacations v on e.employeeId = v.employeeId
group by e.employeeId, e.maxVacationDays
having e.maxVacationDays < count(v.*)

【讨论】：

【解决方案4】：

SELECT e.EmployeeId
        ,COUNT(v.date_vacation_day_taken) TotalDaysTaken
        ,e.maxVacationDays MaxDaysAllowed
FROM Employees e
    INNER JOIN vacations v 
        ON v.employeeId = e.employeeId
WHERE e.isactive = true
GROUP BY e.EmployeeId, e.maxVacationDays, e.isactive
HAVING COUNT(v.date_vacation_day_taken) > e.maxVacationDays

【讨论】：