Question

I am trying to do a FULL OUTER JOIN in MySQL and as we all know that is not possible with their syntax. So, like any normal tinkerer I am using:

(T1 LEFT OUTER JOIN T2) UNION (T1 RIGHT OUTER JOIN T2)

Now here’s the catch! Each of the individual joins (left and right) work like a charm, but together they give an error (1064: syntax error) and I am prompted to check my MySQL Server manual for correct syntax.

Here’s the code:

(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)

Again, the two left and right joins work individually but seem to generate a syntax error if put together with the UNION operator. Any ideas? Are there name collisions? Or is a FULL OUTER JOIN not possible in this case?

Any feedback is very much appreciated! Also, please excuse the triviality of the question (if it is trivial).

EDIT:

"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)