我的SQL語法中的另一個錯誤？

Question

我想知道關於另一個語法錯誤：

SELECT * FROM forum_question 
    WHERE category='art' 
     LEFT JOIN forum_answer ON (forum_question.id = forum_answer.question_id) 
    GROUP BY forum_question.id 
ORDER BY a_datetime DESC; 

我得到的錯誤是這樣的：

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 'LEFT JOIN forum_answer ON (forum_question.id = forum_answer.question_id) GROUP B' at line 1

感謝。

Answer 1

WHERE子句應該在FROM子句之後。 JOIN語句是FROM條款

SELECT * 
FROM forum_question 
     LEFT JOIN forum_answer 
      ON (forum_question.id = forum_answer.question_id) 
WHERE category='art' 
GROUP BY forum_question.id 
ORDER BY a_datetime DESC; 

Answer 2

首先join的一部分，然後使用where條款：

SELECT * FROM forum_question 
    LEFT JOIN forum_answer ON (forum_question.id = forum_answer.question_id) 
    WHERE forum_question.category='art' 
    GROUP BY forum_question.id 
    ORDER BY a_datetime DESC; 

Answer 3

的WHERE條款應是JOIN條款後

SELECT * 
FROM forum_question 
     LEFT JOIN forum_answer 
      ON (forum_question.id = forum_answer.question_id) 
WHERE category='art' 
GROUP BY forum_question.id 
ORDER BY a_datetime DESC;