多个 case 语句 return 1 列多行

Question

我需要评估两组时间戳并创建 1 个可以包含多行的列。更复杂的是，我需要使用函数来收集这些时间戳。我想要什么：

SELECT DISTINCT

mpd.ccn AS CCN,
mpd.date AS Date,
[functionAStartTime] AS A_Start,
[functionAStopTime] AS A_Stop,
[functionBStartTime] AS B_Start,
[functionBStopTime] AS B_Stop,
mpd.fac AS Facility,
bmpi.mod AS Module,
CASE WHEN [functionAStartTime] <= '05:59' AND [functionAStopTime] >= '00:00' THEN 'A' END AS TimeGroup,
CASE WHEN [functionBStartTime] <= '05:59' AND [functionBStopTime] >= '00:00' THEN 'A' END AS TimeGroup,
CASE WHEN [functionAStartTime] <= '11:59' AND [functionAStopTime] >= '06:00' THEN 'B' END AS TimeGroup,
CASE WHEN [functionBStartTime] <= '11:59' AND [functionBStopTime] >= '06:00' THEN 'B' END AS TimeGroup,
CASE WHEN [functionAStartTime] <= '17:59' AND [functionAStopTime] >= '12:00' THEN 'C' END AS TimeGroup,
CASE WHEN [functionBStartTime] <= '17:59' AND [functionBStopTime] >= '12:00' THEN 'C' END AS TimeGroup,
CASE WHEN [functionAStartTime] <= '23:59' AND [functionAStopTime] >= '18:00' THEN 'D' END AS TimeGroup,
CASE WHEN [functionBStartTime] <= '23:59' AND [functionBStopTime] >= '18:00' THEN 'D' END AS TimeGroup

FROM

bmpi,
mpd

WHERE

mpd.pid = bmpi.pid
AND mpd.cec = bmpi.cec

每个 CCN 可以有一组或两组时间戳，并且任一组可以跨越多个组。这显然会创建多个列（Time_Group、Time_Group_1、Time_Group_3 等）我需要一个 "Time Group" 列，每个结果单独一行。如：

CCN   |  Date    | A_Start | A_Stop | B_Start | B_Stop | Facility | Module | Time Group
1234  | 01/01/01 | 07:00   | 12:00  | 17:00   | 21:00  | WPDH     | 0012   | B
1234  | 01/01/01 | 07:00   | 12:00  | 17:00   | 21:00  | WPDH     | 0012   | C
1234  | 01/01/01 | 07:00   | 12:00  | 17:00   | 21:00  | WPDH     | 0021   | C
1234  | 01/01/01 | 07:00   | 12:00  | 17:00   | 21:00  | WPDH     | 0021   | D
4321  | 02/02/02 | 02:00   | 03:00  | 13:00   | 14:00  | ABCD     | 0012   | A
4321  | 02/02/02 | 02:00   | 03:00  | 13:00   | 14:00  | ABCD     | 0021   | C
0001  | 03/03/03 | 06:00   | 08:00  | NULL    | NULL   | WPDH     | 0012   | B

我一直在自学，在我需要的时候搜索我需要的东西，所以非常感谢一个例子和解释。

Answer 1

所以 CASE 语句是一种在 SQL 中执行 "if - then - else" 逻辑的方法，而不是获得多个结果的方法。

我认为您需要一个子查询，将每个时间组值作为单独的列，然后主查询将 UNPIVOT 这些列。这样的事情可能会奏效：

SELECT 
    CCN,
    [Date],
    A_Start,
    A_Stop,
    B_Start,
    B_Stop,
    Facility,
    Module,
    TimeGroup,
    TimeGroupValues
FROM
    (
    SELECT DISTINCT
        mpd.ccn AS CCN,
        mpd.date AS [Date],
        [functionAStartTime] AS A_Start,
        [functionAStopTime] AS A_Stop,
        [functionBStartTime] AS B_Start,
        [functionBStopTime] AS B_Stop,
        mpd.fac AS Facility,
        bmpi.mod AS Module,
        CASE 
            WHEN [functionAStartTime] <= '05:59' AND [functionAStopTime] >= '00:00' 
            THEN 'A' 
            WHEN [functionBStartTime] <= '05:59' AND [functionBStopTime] >= '00:00' 
            THEN 'A' 
            END AS TimeGroupA,
        CASE 
            WHEN [functionAStartTime] <= '11:59' AND [functionAStopTime] >= '06:00' 
            THEN 'B' 
            WHEN [functionBStartTime] <= '11:59' AND [functionBStopTime] >= '06:00' 
            THEN 'B' 
            END AS TimeGroupB,
        CASE 
            WHEN [functionAStartTime] <= '17:59' AND [functionAStopTime] >= '12:00' 
            THEN 'C' 
            WHEN [functionBStartTime] <= '17:59' AND [functionBStopTime] >= '12:00' 
            THEN 'C' 
            END AS TimeGroupC,
        CASE 
            WHEN [functionAStartTime] <= '23:59' AND [functionAStopTime] >= '18:00' 
            THEN 'D'
            WHEN [functionBStartTime] <= '23:59' AND [functionBStopTime] >= '18:00' 
            THEN 'D' 
            END AS TimeGroupD
    FROM
        bmpi
    JOIN
        mpd
    ON
        mpd.pid = bmpi.pid
    AND 
        mpd.cec = bmpi.cec
    ) AS u
    UNPIVOT
        (TimeGroup FOR TimeGroupValues IN
            (
                TimeGroupA, 
                TimeGroupB, 
                TimeGroupC, 
                TimeGroupD
            )
        ) AS p

多个 case 语句 return 1 列多行

Multiple case statements return 1 column with multiple rows

sql

multiple-columns

alias

unpivot

case-when