Mysql - 我可以获取子选择结果并在 WHERE 子句中使用它吗？
我想在 where 子句中获取并使用从 MySQL 中的子选择返回的值。 这可能吗？ 似乎没有必要将子查询写出两次——但是如果我需要的话，MySQL 是否足够聪明，只运行一次？
我尝试了以下方法，但不起作用：
SELECT
(SELECT 1 FROM table WHERE somereallycomplicatedclause = 'something')
AS subselectresult
FROM content WHERE subselectresult = 1
这会产生此错误：
#1054 - Unknown column 'subselectresult' in 'where clause'
谢谢
I want to both fetch and use in a where clause the value returned from a sub-select in MySQL. Is this possible? It seems unecessary to write the sub-query out twice - however if I need to, will MySQL be clever enough to only run it one?
I have tried the following which does not work:
SELECT
(SELECT 1 FROM table WHERE somereallycomplicatedclause = 'something')
AS subselectresult
FROM content WHERE subselectresult = 1
This generates this error:
#1054 - Unknown column 'subselectresult' in 'where clause'
Thanks
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不能在 WHERE 子句中使用列别名。 尝试将其放入 HAVING 中，然后它应该可以工作。
这里的解释： http://dev.mysql.com /doc/refman/5.0/en/problems-with-alias.html
you can't use column aliases in a WHERE clause. try putting it in HAVING and it should work then.
Explanation here: http://dev.mysql.com/doc/refman/5.0/en/problems-with-alias.html
您显示的查询很奇怪。 您可以通过这种方式获得相同的结果（交叉产品）：
我认为您应该更多地说明您尝试解决的问题（例如，子查询和联系人表之间的链接是什么）？
Your query as you displayed is strange. You can achieve the same result this way (cross product):
I think you should say more about what do you try to solve (e.g. what is the link between the sub query and the contacts table)?