MySQL查询员工的可用性

我有一张员工表，所有员工都可以在多个部门工作。但是，一旦某个区段在该日期被预订，则无法在该日期的其他区段中预订该区段

员工表为Employees

id_resources    id_sections EmployeeName    Section
28                25          Mark          Section Two
28                26          Mark          Section Three
28                28          Mark          Section Four
28                29          Mark          Section Five
28                53          Mark          Section Six
28                64          Mark          Section Seven
28                74          Mark          Section Eight
28                76          Mark          Section Nine
29                30          Blair         Section One
29                47          Blair         Section Two
29                49          Blair         Section Three
30                82          Sam           Section One
30                25          Sam           Section Two
30                28          Sam           Section Three
30                29          Sam           Section Four
31                18          David         Section Eleven
31                19          David         Section One
31                22          David         Section Two
31                25          David         Section Three

id_resources    id_sections startdate   enddate
28                 25      2016-09-09   2016-09-09
28                 26      2016-09-20   2016-09-20
28                 28      2016-10-17   2016-10-17
30                 82      2016-10-18   2016-10-18
30                 25      2016-10-28   2016-10-28
29                 30      2016-11-02   2016-11-02
29                 47      2016-11-07   2016-11-07
29                 49      2016-11-01   2016-11-01
29                 58      2017-01-09   2017-01-09

然后我的预订表是预订

id_resources    id_sections EmployeeName    Section
28                25          Mark          Section Two
28                26          Mark          Section Three
28                28          Mark          Section Four
28                29          Mark          Section Five
28                53          Mark          Section Six
28                64          Mark          Section Seven
28                74          Mark          Section Eight
28                76          Mark          Section Nine
29                30          Blair         Section One
29                47          Blair         Section Two
29                49          Blair         Section Three
30                82          Sam           Section One
30                25          Sam           Section Two
30                28          Sam           Section Three
30                29          Sam           Section Four
31                18          David         Section Eleven
31                19          David         Section One
31                22          David         Section Two
31                25          David         Section Three

id_resources    id_sections startdate   enddate
28                 25      2016-09-09   2016-09-09
28                 26      2016-09-20   2016-09-20
28                 28      2016-10-17   2016-10-17
30                 82      2016-10-18   2016-10-18
30                 25      2016-10-28   2016-10-28
29                 30      2016-11-02   2016-11-02
29                 47      2016-11-07   2016-11-07
29                 49      2016-11-01   2016-11-01
29                 58      2017-01-09   2017-01-09

因此，我的问题是让员工：

A.）如果一天预订了一个部分，则不适用于所有部分
B.）选择日期范围且没有该范围的预订时，显示员工可用

我可以得到A部分，但不能得到B部分

Select *
FROM employees
LEFT JOIN bookings on employees.id_resources = bookings.id_resources
WHERE
   (Select..... and i get lost here

再次感谢您的帮助

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-李

你应该试试这样的东西：

SELECT employees.*
FROM employees
    LEFT OUTER JOIN bookings 
    ON employees.id_resources = bookings.id_resources 
        AND (
        (startdate BETWEEN $start_range AND $end_range)
        OR 
        (enddate BETWEEN $start_range AND $end_range)
        )
WHERE bookings.id_resources IS NULL

快速解释：我们使用左外连接。。。哪里作为排除项为空。也许对你有帮助

编辑：当您使用左外连接作为排除时，首先，您必须从与目标相反的角度思考。在这里，可以找到一个在两个日期之间有预订的用户。为此，您将有如下查询：

SELECT employees.*
FROM employees
    INNER JOIN bookings 
    ON employees.id_resources = bookings.id_resources 
        AND (startdate BETWEEN $start_range AND $end_range)
        AND (enddate BETWEEN $start_range AND $end_range)

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然后你做相反的事情。

我能问一下为什么你使用id\u资源而不是id\u部分吗？