I have this query, working fine, but it works only if I have data for the two disciplines PORTUGUESE and MATHEMATICS, how can I do that, without harming the result, regardless of whether there are only one or both disciplines I can get the results, it follows below only the part of the query that I think necessary, if I need to put the rest.
-- Campos a selecionar.
SELECT
AVG(IFNULL(pqas.fraction, 0)) * 10 AS MediaPT,
AVG(IFNULL(mqas.fraction, 0)) * 10 AS MediaMT,
gg.finalgrade AS NotaGeral,
u.firstname AS Aluno,
u.username AS Usuario,
u.lastname AS siem,
-- u.id, -- removido
u.department AS Turma,
u.institution AS Escola,
pqc.name AS catp,
mqc.name AS catm
FROM mdl_user u
INNER JOIN mdl_grade_grades gg ON gg.userid = u.id
INNER JOIN mdl_grade_items gi ON gi.'id' = gg.'itemid'
INNER JOIN mdl_question_attempt_steps pqas ON u.id = pqas.userid
INNER JOIN mdl_question_attempts pqa ON pqa.id = pqas.questionattemptid
INNER JOIN mdl_question pq ON pq.id = pqa.questionid
INNER JOIN mdl_quiz_slots pqs ON pqs.questionid = pqa.questionid AND pqs.slot = pqa.slot
INNER JOIN mdl_quiz pquiz ON pquiz.id = pqs.quizid
INNER JOIN mdl_question_categories pqc ON pqc.id = pq.category
INNER JOIN mdl_question_attempt_steps mqas ON u.id = mqas.userid
INNER JOIN mdl_question_attempts mqa ON mqa.id = mqas.questionattemptid
INNER JOIN mdl_question mq ON mq.id = mqa.questionid
INNER JOIN mdl_quiz_slots mqs ON mqs.questionid = mqa.questionid AND mqs.slot = mqa.slot
INNER JOIN mdl_quiz mquiz ON mquiz.id = mqs.quizid
INNER JOIN mdl_question_categories mqc ON mqc.id = mq.category
-- Parte do WHERE para filtrar apenas PORTUGUES nas tabelas p.
WHERE SUBSTR(pqc.name, 8) = "PORTUGUES"
-- Parte do WHERE para filtrar apenas matemática nas tabelas m.
AND SUBSTR(mqc.name, 8) = "MATEMATICA"
-- Final da query.
GROUP BY turma, u.id
ORDER BY turma ASC, 'Aluno' ASC