[英]Using UNION inside of NOT IN
I'm trying to make query using a NOT IN
condition. 我正在尝试使用NOT IN
条件进行查询。 If I use a subquery I got no problem, but when I try to use UNION
to join results from two tables, I got an error. 如果我使用子查询我没有问题,但是当我尝试使用UNION
连接两个表的结果时,我收到了一个错误。
This is what I'm doing: 这就是我正在做的事情:
SELECT *
FROM users
WHERE id NOT IN(
(
SELECT DISTINCT(user_id) AS id
FROM users_table_1
)
UNION
(
SELECT DISTINCT(user_id) AS id
FROM users_table_2
)
)
Is there a way to get what I want using subqueries? 有没有办法通过子查询获得我想要的东西?
I think there's a syntax issue in your code. 我认为您的代码中存在语法问题。 Did you try to put UNION
inside the subquery? 你试图将UNION
放在子查询中吗?
SELECT *
FROM users
WHERE id NOT IN(
SELECT user_id AS id
FROM users_table_1
UNION
SELECT user_id
FROM users_table_2
)
The DISTINCT
keyword is redundant (see @ypercube's comment). DISTINCT
关键字是多余的(请参阅@ ypercube的评论)。
@yasir Actually, this is not a real syntax problem (the same syntax is accepted by other SQL databases), but rather a limitation in MySQL query parser, implemented using the bison parser generator . @yasir实际上,这不是一个真正的语法问题(其他SQL数据库接受相同的语法),而是使用bison解析器生成器实现的 MySQL查询解析器的限制。
The error stems from the parser's need to decide between two possible parse trees, since both SELECT subqueries and sub-expressions may be enclosed in parentheses. 该错误源于解析器需要在两个可能的解析树之间进行决策,因为SELECT子查询和子表达式都可以括在括号中。 Therefore a minimal solution here would be to remove the parens only from the first subquery, ie: 因此,这里的最小解决方案是仅从第一个子查询中删除parens,即:
SELECT *
FROM users
WHERE id NOT IN(
SELECT user_id AS id
FROM users_table_1
UNION
(
SELECT user_id
FROM users_table_2
)
)
This way you "help" mysql disambiguate between the two possible parse trees. 这样你就可以“帮助”mysql消除两个可能的解析树之间的歧义。 In bison lingo, that would avoid the shift/reduce conflict. 在野牛术语中,这将避免转移/减少冲突。
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