mysql - Mysql内部连接两次并在两个连接上使用WHERE

Question

在 MySQL 中，我想直接（连接表）或通过另一个连接表（）SELECT A.* FROM A满足内部连接条件。谁能指出获得结果的正确方法？BCWHERE B.field = myvalue

我有以下表格：A、B、C，关联如下（A 连接 B，B 连接 C，A 连接 C）：

      B
    /   \
   A --- C

它看起来很简单，但是当我运行以下代码时我得到一个空集，即使当我将搜索限制为仅加入 B 到 C 时我得到了结果：

SELECT A.* FROM A
INNER JOIN C ON C.id = A.c_id
INNER JOIN B AS B_thru_C ON B_thru_C.id = C.b_id
INNER JOIN B AS B_from_A ON B_from_A.id = A.b_id
WHERE B_thru_C.field = 'myvalue' OR B_from_A.field = 'myvalue';
# yields an empty set

SELECT A.* FROM A
INNER JOIN C ON C.id = A.c_id
INNER JOIN B AS B_thru_C ON B_thru_C.id = C.b_id
WHERE B_thru_C.field = 'myvalue';
# yields results

Answer 1

这个怎么样？

SELECT A.* FROM A
LEFT OUTER JOIN C ON C.id = A.c_id
INNER JOIN B ON B.id = A.b_id OR B.id = C.b_id
WHERE B.field = 'myvalue';