mysql - MySQL 中的 FULL OUTER JOIN 语法问题（左联合右）

Question

我正在尝试在 MySQL 中进行 FULL OUTER JOIN，我们都知道这是不可能的。所以，就像我正在使用的任何普通修补匠一样：

(T1 左外连接 T2) UNION (T1 右外连接 T2)

现在这是问题所在！每个单独的连接（左和右）都像一个魅力，但它们一起给出一个错误（1064：语法错误），并且提示我检查我的 MySQL 服务器手册以获取正确的语法。

这是代码：

(SELECT 
    *
FROM
    result LEFT OUTER JOIN 
    ((SELECT * FROM SQA AS sqa JOIN SA AS sa USING (sa_oid) WHERE sqa.sq_oid = 1)
    AS tmp1) ON tmp1.sa_oid = result.re_as

WHERE
    result.re_p = 1 AND 
    result.re_s = 1 AND
    result.re_q = 1)

UNION

(SELECT 
    *
FROM
    result RIGHT OUTER JOIN 
    ((SELECT * FROM SQA AS sqa JOIN SA AS sa USING (sa_oid) WHERE sqa.sq_oid = 1)
    AS tmp2) ON tmp2.sa_oid = result.re_as

WHERE
    result.re_p = 1 AND 
    result.re_s = 1 AND
    result.re_q = 1)

同样，两个左连接和右连接单独工作，但如果与 UNION 运算符放在一起，似乎会产生语法错误。有任何想法吗？有名称冲突吗？或者在这种情况下不可能进行 FULL OUTER JOIN ？

非常感谢任何反馈！另外，请原谅这个问题的琐碎（如果它是琐碎的）。

编辑：

"Error Code: 1064
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ON tmp2.sa_oid = result.re_as

    WHERE
        result.re_p = 1 AND 
        result.re' at line 20"

Answer 1

Try this:

(SELECT 
    *
FROM
    result LEFT OUTER JOIN 
    (SELECT * FROM surveyquestion_answers AS sqa JOIN surveyanswer AS sa USING (sa_oid) WHERE sqa.sq_oid = 1)
    AS tmp1 ON tmp1.sa_oid = result.re_answer

WHERE
    result.re_page = 1 AND 
    result.re_survey = 1 AND
    result.re_question = 1)

UNION

(SELECT 
    *
FROM
    result RIGHT OUTER JOIN 
    (SELECT * FROM surveyquestion_answers AS sqa JOIN surveyanswer AS sa USING (sa_oid) WHERE sqa.sq_oid = 1)
    AS tmp2 ON tmp2.sa_oid = result.re_answer

WHERE
    result.re_page = 1 AND 
    result.re_survey = 1 AND
    result.re_question = 1)