Question

我的查询中有2行，用于从表中选择最小值和最大值。返回最多只有2行，但是如果只返回1行，我不希望第二行返回任何内容。

IE：

MAX(CASE WHEN bd.DayText = 'Tuesday' and bd.BookingDuration = 3 
and CONVERT(time(0), bd.StartTime) < CONVERT(time(0), '12:00:00') 
AND bd.NoOfHOurs < 5.5 and s.PrimarySchool = 1 THEN bd.ID ELSE NULL END)
"TuesdayHourlyAM",

MIN(CASE WHEN bd.DayText = 'Tuesday' and bd.BookingDuration = 3 
and CONVERT(time(0), bd.StartTime) < CONVERT(time(0), '12:00:00') 
AND bd.NoOfHOurs < 5.5 and s.PrimarySchool = 1 THEN bd.ID ELSE NULL END)
"TuesdayHourlyAM2",

因此，如果返回第1行，则TuesdayHourlyAM2应返回null。

有什么想法吗？

谢谢

Answer 1

尝试将其包装在case语句中：

(case when count(*) > 1
      then MIN(CASE WHEN bd.DayText = 'Tuesday' and bd.BookingDuration = 3 and
                         CONVERT(time(0), bd.StartTime) < CONVERT(time(0), '12:00:00') AND
                         bd.NoOfHOurs < 5.5 and s.PrimarySchool = 1
                    THEN bd.ID ELSE NULL
               END)
 end) as TuesdayHourlyAM2

SQL MIN和MAX只有一行时

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