Question

我正在查询预订系统，我需要确定所有预订时间表（代表定期预订），其中指定日期范围的所有预订都已取消。为什么以下查询会在取消的指定日期范围内向我提供包含预订的预订时间表？

SELECT DISTINCT b.BookingScheduleId FROM Booking b
 WHERE b.CancellationStatus = 1
   AND b.[Date] BETWEEN '01-Nov-14' AND '31-Dec-14'
   AND NOT EXISTS (
       SELECT * FROM Booking ref
        WHERE ref.BookingScheduleId = b.BookingScheduleId
          AND ref.[Date] BETWEEN '01-Nov-14' AND '31-Dec-14'
          AND b.CancellationStatus = 0
       )
   AND b.BookingScheduleId IS NOT NULL

Answer 1

我首先使用ANSI标准日期编写查询：

SELECT DISTINCT b.BookingScheduleId
FROM Booking b
WHERE b.CancellationStatus = 1 AND
      b.[Date] BETWEEN '2014-01-14' AND '2014-12-31' AND
      NOT EXISTS (SELECT 1
                  FROM Booking ref
                  WHERE ref.BookingScheduleId = b.BookingScheduleId AND
                        ref.[Date] BETWEEN '2014-01-14' AND '2014-12-31' AND
                        b.CancellationStatus = 0
 -----------------------^
                 ) AND
      b.BookingScheduleId IS NOT NULL;

然后我会注意带下划线的部分并稍微改写一下查询：

SELECT s.BookingScheduleId
FROM (SELECT DISTINCT BookingScheduleId
      FROM Booking b
      WHERE b.CancellationStatus = 1 AND
            b.[Date] BETWEEN '2014-01-14' AND '2014-12-31' AND
            b.BookingScheduleId IS NOT NULL
     ) s
WHERE  NOT EXISTS (SELECT 1
                   FROM Booking ref
                   WHERE ref.BookingScheduleId = s.BookingScheduleId AND
                         ref.[Date] BETWEEN '2014-01-14' AND '2014-12-31' AND
                         ref.CancellationStatus = 0
                  );

我更喜欢做过滤和不同的子查询。它可能可能更快（虽然我不知道没有查看执行计划或测量性能），但我更清楚，因为子查询获取候选计划而外部计划进行过滤使用not exists。顺便说一句，您也可以将此查询短语作为聚合查询，但我将其保留为此格式，因为这似乎是您的意图。

SQL - 搜索预订时间表，其中所有日期范围的预订都已取消

1 个答案: