Question

我的任务是创建一个支持Web的数据库，客户可以在其中预订露营地场地。

我目前正在处理一个SQL查询，以检查某个日期内可用的投标。

我有一个'Pitch'表，其中包含type_id和StartDate列，以及一个包含EndDate和SELECT Pitch FROM Pitch AS p WHERE Pitch NOT IN ( SELECT Pitch From Booking As b WHERE b.Pitch IS NOT NULL AND b.Pitch = p.pitch AND (StartDate >= 15/06/2015 AND EndDate <= 20/06/2015) );列的“预订”表格。我目前有这个：

TTTAttributedLabel

Answer 1

首先，您应该在引用表格时取出“AS”关键字。这通常只用于列。然后，不要尝试加入您的子查询。它可能看起来像这样：

SELECT PITCH 
FROM PITCH 
WHERE PITCH NOT IN (
    SELECT PITCH FROM BOOKING
    WHERE WHERE STARTDATE >= 15/06/2015 --verify syntax of date
      AND ENDDATE <= 20/06/2015 );

虽然我不建议将列命名为与表相同。

Answer 2

你也可以像这样使用JOIN （仅返回两个日期期间可用的投球）：

SELECT DISTINCT
    p.pitch
FROM
    Pitch p
    JOIN
    Booking b ON p.pitch = b.pitch
WHERE
    b.StartDate >= '2015-06-15' 
AND b.EndDate <= '2015-06-20'

或像这样使用EXISTS：

SELECT DISTINCT
    p.pitch
FROM
    Pitch p
WHERE
    EXISTS(    -- or add a `NOT` at first to return only the pitches that are not available during the two dates.
        SELECT 1
        FROM Booking b
        WHERE
            p.pitch = b.pitch
        AND b.StartDate >= '2015-06-15'
        AND b.EndDate <= '2015-06-20'

SQL查询，按给定日期范围选择可用的投标

2 个答案: