需要一些协助来进行表格连接

Question

我有两个SQL表，我想加入它们以显示如下所示的时间表：

WorkID WorkDesc TaskOneStart TaskOneEnd  TaskTwoStart TaskTwoEnd TaskThreeStart TaskThreeEnd TaskFourStart TaskFourEnd
1      Job 1    10:00        11:00      11:00 12:00  13:00      14:00       15:00       16:00
2      Job 2    10:00        11:00      11:00 12:00  13:00      14:00       NULL        NULL
3      Job 3    10:00        11:00      NULL  NULL   NULL       NULL        NULL        NULL
4      Job 4    10:00        11:00      NULL  NULL   13:00      14:00        NULL       NULL

Table Work
  ID    WorkDesc
  1     Job 1
  2     Job 2
  3     Job 3
  4     Job 4

Table Task
  ID   WorkID   TaskDesc      StartTime  EndTime
  1    1        TaskOne      10:00        11:00
  2    1        TaskTwo      11:00        12:00
  3    1        TaskThree    13:00        14:00
  4    1        TaskFour     15:00        16:00
  5    2        TaskOne      10:00        11:00
  6    2        TaskTwo      11:00        12:00
  7    2        TaskThree    13:00        14:00
  8    3        TaskOne      10:00        11:00
  9    4        TaskOne      10:00        11:00
  10   4        TaskThree    13:00        14:00

至少可以说，我是SQL新手。 我所有的尝试都导致该表具有300多个行而不是4行。任何帮助将不胜感激。

Answer 1

假设有固定数量的任务：

SELECT  W.ID WorkID,
        W.WorkDesc,
        MIN(CASE WHEN TaskDesc = 'TaskOne' THEN StartTime END) TaskOneStart,
        MIN(CASE WHEN TaskDesc = 'TaskOne' THEN EndTime END) TaskOneEnd,
        MIN(CASE WHEN TaskDesc = 'TaskTwo' THEN StartTime END) TaskTwoStart,
        MIN(CASE WHEN TaskDesc = 'TaskTwo' THEN EndTime END) TaskTwoEnd,
        MIN(CASE WHEN TaskDesc = 'TaskThree' THEN StartTime END) TaskThreeStart,
        MIN(CASE WHEN TaskDesc = 'TaskThree' THEN EndTime END) TaskThreeEnd,
        MIN(CASE WHEN TaskDesc = 'TaskFour' THEN StartTime END) TaskFourStart,
        MIN(CASE WHEN TaskDesc = 'TaskFour' THEN EndTime END) TaskFourEnd
FROM dbo.Work W
LEFT JOIN dbo.Task T
    ON W.ID = T.WorkID
GROUP BY W.ID WorkID,
         W.WorkDesc
ORDER BY W.ID WorkID,
         W.WorkDesc