Question

我有这张桌子：

// QandA
+----+-----------+-----------------------+-----------+------+---------+
| id |   title   |        content        |  related  | type | deleted |
+----+-----------+-----------------------+-----------+------+---------+
| 1  | question1 | content of question1  | 1         | 0    | 0       |
| 2  | answer1-1 | content of answer1-1  | 1         | 1    | 0       |
| 3  | question2 | content of question2  | 3         | 0    | 0       |
| 4  | answer1-2 | content of answer1-2  | 1         | 1    | 0       |
| 5  | answer2-1 | content of answer2-1  | 3         | 1    | 0       |
+----+-----------+-----------------------+-----------+------+---------+

related 列包含自己所有答案的问题ID。
type 列的问题为0，问题为1。
deleted 列为0，当问题\答案未被删除时，1会被删除。

这也是我的疑问：

SELECT * FROM QandA WHERE related = :id AND deleted = 0

我的问题：如何实施此条件：

如果deleted为1那么：

如果type是0 （这是一个问题）则选择
如果type是1 （这是答案）那么只有不选择该行

Answer 1

我想你想要排除已删除问题的所有答案：

1）删除应为0

2）它应该是一个问题或（如果是答案）它不应该属于已删除的问题

SELECT * FROM QandA qa
WHERE 
    related = :id
    AND deleted = 0
    AND (
        type = 0
        OR NOT EXISTS (
            SELECT * FROM QandA q WHERE q.id = qa.related AND q.deleted
        )
    )

如果条件错误，我如何打破选择？

1 个答案: