MySql会排除具有特定ID的结果吗？

Question

这是我的SQL语句

            SELECT * FROM schedule
            WHERE teacher_id = '$teacher_id'
            AND event_id <> '$event_id'
            AND seconds_start = '$start_time'
            OR (seconds_start < '$start_time' AND seconds_end > '$start_time')
            OR (seconds_start < '$end_time' AND seconds_end >= '$end_time')

正如您所看到的，我想要排除任何带有特定ID的结果，但这似乎不起作用，因为......

这不应该像预期的那样行事吗？

Answer 1

你显然不理解Operator Precedence

您很少在同一条指令中混合AND和OR运算符，而不用括号指定其范围。

在括号后正确缩进代码也有助于理解您的查询：

    SELECT * FROM schedule
    WHERE teacher_id = '$teacher_id'
      AND event_id <> '$event_id'
      AND ( 
             seconds_start = '$start_time'
         OR (seconds_start < '$start_time' AND seconds_end > '$start_time')
         OR (seconds_start < '$end_time' AND seconds_end >= '$end_time')
        )

Answer 2

也许您需要对second_start

进行分组

    SELECT * FROM schedule
    WHERE teacher_id = '$teacher_id'
    AND event_id <> '$event_id'
    AND (seconds_start = '$start_time'
    OR (seconds_start < '$start_time' AND seconds_end > '$start_time')
    OR (seconds_start < '$end_time' AND seconds_end >= '$end_time'))

Answer 3

您的OR部分会使您的陈述忽略您对event_id的限制。

正如Jon Stirling指出的那样，你需要相应地设置括号。

    SELECT * FROM schedule
    WHERE teacher_id = '$teacher_id'
    AND event_id <> '$event_id'
    AND (
        seconds_start = '$start_time'
        OR (seconds_start < '$start_time' AND seconds_end > '$start_time')
        OR (seconds_start < '$end_time' AND seconds_end >= '$end_time')
    )