Question

I have this query:

SELECT
    course_category.id      AS languageId,
    course_category.code    AS languageCode,
    course_category.name    AS languageName,
    (
        SELECT
            SUM(gradebook_result.score)
        FROM
            gradebook_result
        JOIN
            gradebook_evaluation ON  gradebook_evaluation.id=gradebook_result.evaluation_id
        JOIN
            gradebook_category ON gradebook_category.id=gradebook_evaluation.category_id
        WHERE
            gradebook_category.course_code=course_category.code

    ) AS languageWordsTranslated
FROM
    course_category
WHERE
    course_category.code != 'GEN'
ORDER BY
    name
ASC

The problem occurs inside the nested SELECT where I get an error referencing the course_category table from within the SELECT on line:

WHERE
    gradebook_category.course_code=course_category.code

Giving error:

Unknown column 'course_category.code' in 'where clause'

I have done this query before with other projects the only difference is that this one has joins within it. Any ideas?

EDIT: I removed the joins and hardcoded:

WHERE
    course_category.code = 'ARA'

Seems like the joins mess it up, any way to fix that??

Answer 1

Try to do it a bit different way, using subquery and joining to it:

SELECT
    course_category.id      AS languageId,
    course_category.code    AS languageCode,
    course_category.name    AS languageName,
    t.total AS languageWordsTranslated
FROM
    course_category
JOIN (
    SELECT gradebook_category.course_code, SUM(gradebook_result.score) as total
    FROM gradebook_result
    JOIN gradebook_evaluation ON  gradebook_evaluation.id=gradebook_result.evaluation_id
    JOIN gradebook_category ON gradebook_category.id=gradebook_evaluation.category_id
    GROUP BY gradebook_category.course_code
) t ON t.course_code = course_category.code
WHERE
    course_category.code != 'GEN'
ORDER BY
    name
ASC