Question

我有一个相当复杂的查询，它根据子查询对结果进行排序。这很好用。查询如下。

 SELECT enrollments.*, users.*
 FROM enrollments
 INNER JOIN users
 ON enrollments.user_id = users.id
 WHERE enrollments.preview = FALSE
 ORDER BY (
   SELECT COUNT(progress_tracker)
   FROM progress_tracker
   WHERE progress_tracker.enrollment_id = enrollments.id
   AND progress_tracker.completed = TRUE
 )

这里我从“用户”和“注册”表中选择字段。理想情况下，我想在sql结果中再添一个字段。该字段表示ORDER BY sql的结果：

SELECT COUNT(progress_tracker)
FROM progress_tracker
WHERE progress_tracker.enrollment_id = enrollments.id
AND progress_tracker.completed = TRUE

是否可以从此查询中创建一个字段并将其附加到每行的结果中？该行的名称将恰当地称为enrollment_progress_tracker_completed_count。如果是这样，我该怎么做？

Answer 1

将子查询添加到select，然后使用它进行排序：

SELECT e.*, u.*,
       (SELECT COUNT(*)
        FROM progress_tracker pt
        WHERE pt.enrollment_id = e.id AND pt.completed = TRUE
       ) as newcol
FROM enrollments e INNER JOIN
     users u
     ON e.user_id = u.id
WHERE e.preview = FALSE
ORDER BY newcol;

Answer 2

使用临时表

rule

从子查询中追加字段

2 个答案: