Question

我在计划应用程序中有两个SQL查询，以帮助检查员工的可用性。我需要执行左外连接，但我似乎无法使语法正确。

第一个查询获取在给定时间可用的员工列表，并具有执行要安排的任务的正确资格。

    SELECT e.e_id FROM AppointmentTypes a1
    INNER JOIN EmployeeQualifications eq ON a1.type_id = eq.ea_id
    INNER JOIN Employees e ON e.e_id = eq.e_id
    INNER JOIN EmployeeAvaliable ea ON ea.e_id = e.e_id
    INNER JOIN EmployeeTimes et ON et.time_id = ea.time_id
    INNER JOIN AppointmentTimes a2
    INNER JOIN TypeTimes tt ON tt.time_id = a2.time_id AND tt.type_id = a1.type_id
    WHERE et.wednesday = '1'
    AND a1.type_id = '4'
    AND et.start <= '10:00:00' 
    AND et.end > '10:00:00'

第二个查询获取已在此时安排了事件的员工列表。

    SELECT e.e_id
    FROM AppointmentTypes atp 
    INNER JOIN Appointments a ON atp.type_id = a.type_id 
    INNER JOIN EmployeesAttending ea ON a.a_id = ea.a_id 
    INNER JOIN Employees e ON e.e_id = ea.e_id 
    WHERE date(a.start_time) = '2014-12-10'
    AND ADDTIME(time(a.start_time),'02:00:00') > '10:00:00'
    AND time(a.start_time) < '12:00:00'

左外连接这些应该给我一份合格，可用且当时没有安排活动的员工名单。

Answer 1

没有左外连接会给你左边的所有东西以及右边的可以连接的东西。在他们无法做到的地方。

我认为你要做的是让第一组中的所有内容都不在第二组中。

SELECT e.e_id FROM AppointmentTypes a1
INNER JOIN EmployeeQualifications eq ON a1.type_id = eq.ea_id
INNER JOIN Employees e ON e.e_id = eq.e_id
INNER JOIN EmployeeAvaliable ea ON ea.e_id = e.e_id
INNER JOIN EmployeeTimes et ON et.time_id = ea.time_id
INNER JOIN AppointmentTimes a2
INNER JOIN TypeTimes tt ON tt.time_id = a2.time_id AND tt.type_id = a1.type_id
WHERE et.wednesday = '1'
AND a1.type_id = '4'
AND et.start <= '10:00:00' 
AND et.end > '10:00:00'
AND e.e_id NOT IN (
    SELECT e.e_id
FROM AppointmentTypes atp 
INNER JOIN Appointments a ON atp.type_id = a.type_id 
INNER JOIN EmployeesAttending ea ON a.a_id = ea.a_id 
INNER JOIN Employees e ON e.e_id = ea.e_id 
WHERE date(a.start_time) = '2014-12-10'
AND ADDTIME(time(a.start_time),'02:00:00') > '10:00:00'
AND time(a.start_time) < '12:00:00'
)

Answer 2

试试这个：

SELECT e.e_id 
FROM AppointmentTypes a1
INNER JOIN EmployeeQualifications eq ON a1.type_id = eq.ea_id
INNER JOIN Employees e ON e.e_id = eq.e_id
INNER JOIN EmployeeAvaliable ea ON ea.e_id = e.e_id
INNER JOIN EmployeeTimes et ON et.time_id = ea.time_id
INNER JOIN AppointmentTimes a2
INNER JOIN TypeTimes tt ON tt.time_id = a2.time_id AND tt.type_id = a1.type_id
LEFT OUTER JOIN (SELECT DISTINCT e.e_id
                 FROM AppointmentTypes atp 
                 INNER JOIN Appointments a ON atp.type_id = a.type_id 
                 INNER JOIN EmployeesAttending ea ON a.a_id = ea.a_id 
                 INNER JOIN Employees e ON e.e_id = ea.e_id 
                 WHERE DATE(a.start_time) = '2014-12-10' AND 
                       ADDTIME(TIME(a.start_time),'02:00:00') > '10:00:00' AND 
                       TIME(a.start_time) < '12:00:00'
                ) AS A ON e.e_id = A.e.e_id  
WHERE et.wednesday = '1' AND a1.type_id = '4' AND 
      et.start <= '10:00:00' AND et.end > '10:00:00' AND
      A.e.e_id IS NULL;

在两个MySQL查询上执行左外连接？

2 个答案: