Question

i have this query:

SELECT `completed`.`ID` AS `ID`,`completed`.`level` AS `level`,`completed`.`completed_in` AS `completed_in`, COUNT(1) AS `right_answers_num` 
FROM `completed` 
INNER JOIN `history` ON `history`.`ID` = `completed`.`ID` 
INNER JOIN `questions` ON `questions`.`ID` = `history`.`question`
WHERE `completed`.`student_id` = '1' AND `questions`.`answer` = `history`.`answer`       
GROUP BY `completed`.`ID` 
ORDER BY `completed`.`completed_in` DESC

what i need is to get info of each test in completed table (id,level,completed_in,right_answer_num)
the problem with that query is that if there is no one right answer(history.answer = questions.answer) then it doesn’t return the row, while it should return the row(id,level,completed_in) and the right_answer_num(counter) should be zero..

please help me,, thanks ahead.

Answer 1

SELECT 
    completed.ID AS ID,
    completed.level AS level,
    completed.completed_in AS completed_in, 
    COUNT(questions.answer) AS right_answers_num 
FROM completed
        INNER JOIN history  ON history.ID = completed.ID
        LEFT JOIN questions ON questions.ID = history.question AND questions.answer = history.answer
WHERE 
    completed.student_id = '1'  
GROUP BY 
completed.ID 
ORDER BY completed.completed_in DESC