SELECT cols，（SELECT inner query）AS innercol FROM table WHERE innercol something

Question

只要我避免WHERE stream_json ...这是可以修复的，还是需要JOINS？

SELECT id, stuff, 
    (SELECT count(*) 
    FROM inner_table 
    WHERE inner_table.movie_id = outer_table.id) 
      AS stream_json 
FROM outer_table 
WHERE stream_json != 0 

Answer 1

您可以使用HAVING访问他们不能使用WHERE条款被受理自定义别名

SELECT (SELECT count(*) FROM inner_table 
WHERE inner_table.movie_id = outer_table.id) AS stream_json 
FROM outer_table HAVING stream_json != 0 

See this for reference

Answer 2

您不能在WHERE条件中使用别名。但是，您可以在HAVING条件下使用它。另一种选择是重复整个子查询，但看起来很丑。我建议使用HAVING。

SELECT (SELECT count(*) FROM inner_table 
WHERE inner_table.movie_id = outer_table.id) AS stream_json 
FROM outer_table HAVING stream_json != 0 

Answer 3

正如上面可以使用具有，或者您也可以加入针对其避免相关子查询

SELECT outer_table.id, outer_table.stuff, stream_json 
FROM outer_table 
INNER JOIN 
(
    SELECT movie_id, count(*) AS stream_json 
    FROM inner_table 
    GROUP BY movie_id 
) Sub1 
ON Sub1.movie_id = outer_table.id 

请注意，您不需要在检查stream_json子选择！= 0，这是它隐含在INNER JOIN中

Answer 4

您无法访问同一级别上的列别名。您需要将其包装到派生表中：

select * 
from (
    SELECT id, 
     stuff, 
     (SELECT count(*) 
      FROM inner_table 
      WHERE inner_table.movie_id = outer_table.id) AS stream_json 
    FROM outer_table 
) t 
WHERE stream_json <> 0; 

但是Kickstart的答案可能是解决此问题的更好方法。