Question

SELECT 'Q' AS TYPE, 
       q.question AS value, 
       q.date
  FROM questions q
 WHERE q.user_id =39
UNION ALL 
SELECT 'A' AS TYPE, 
       q.question AS value, 
       a.date
  FROM answers a,
       questions q
 WHERE a.question_id = q.id
   AND WHERE a.user_id =39
ORDER BY `date` DESC

数据库设计：

问题{ID，USER_ID，问题，日期}
答案{ID，question_id，USER_ID，答案，日期}

错误：

1064 - 您的SQL语法出错;检查与MySQL服务器版本对应的手册，以便在'WHERE a'附近使用正确的语法。 user_id = 39 ORDER BY date DESC

Answer 1

查询的下半部分有两个WHERE子句。你需要从字面上删除最后一个字WHERE。您只需要错误描述。

Answer 2

“WHERE”出现两次。其中x = ..... AND ....

Answer 3

有一个额外的地方a.user_id = 39。您只在子句的开头使用关键字WHERE（a.question_id = q.id AND a.user_id = 39）

SELECT 
'Q' AS TYPE , q.question AS value, q.date
FROM questions q
WHERE q.user_id =39
UNION ALL 
SELECT 'A' AS TYPE , q.question AS value, a.date
FROM answers a,questions q
WHERE a.question_id = q.id
AND
a.user_id =39
ORDER BY `date` DESC

Answer 4

当错误试图解释时：对于第二个选择，你只需要放一个“WHERE”。

SELECT 'A' AS TYPE , q.question AS value, a.date
FROM answers a,questions q
WHERE a.question_id = q.id
AND
a.user_id =39

这个UNION ALL mysql查询有什么问题？

4 个答案: