Question

所以我有以下内容：

SELECT bt.CompanyName, 
    AcceptedTable.Count AS AcceptedCount,
    CompletedTable.Count AS CompletedCount,
    SkippedTable.Count AS SkippedCount,
    TotalTable.Count AS TotalCount
FROM (
    SELECT uic.*, uic.Id AS UCId, ic.*, ic.Id AS CompanyId, ic.Name AS CompanyName
    FROM UserChallenges iuc 
    JOIN Users iu ON iuc.UserId = iu.Id 
    JOIN Companies ic ON ic.Id = iu.CompanyId) bt
JOIN (
    SELECT CompanyId AS CompanyId, COUNT(UCId) AS Count
    FROM bt
    GROUP BY CompanyId) TotalTable ON CompletedTable.CompanyId = bt.CompanyId
JOIN (
    SELECT CompanyId AS CompanyId, COUNT(UCId) AS Count
    FROM bt
    WHERE AcceptedAt IS NOT NULL
    GROUP BY CompanyId) AcceptedTable ON CompletedTable.CompanyId = bt.CompanyId
JOIN (
    SELECT CompanyId AS CompanyId, COUNT(UCId) AS Count
    FROM bt
    WHERE DoneStatus IN (1,6)
    GROUP BY CompanyId) CompletedTable ON CompletedTable.CompanyId = bt.CompanyId
JOIN (
    SELECT CompanyId AS CompanyId, COUNT(UCId) AS Count
    FROM bt
    WHERE DoneStatus IN (4)
    GROUP BY CompanyId) SkippedTable ON SkippedTable.CompanyId = bt.CompanyId
GROUP BY bt.CompanyName

目标是使用不同的WHERE子句对同一组数据计算计数。

我尝试了上述方法，因为它简化了查询，而不必在每个子查询中再次执行JOIN。但是似乎不可能，它是Common table expression，在mysql 5.7中不可用。

有什么更好的方法来实现呢？

必须有比这种超长查询更干净的方法。

我也可以使用临时表，尽管我不确定在View中这是个好主意。

Answer 1

您不能在其他派生表的<div class="mat-elevation-z8"> <table *ngIf="dataSource" mat-table class="full-width-table" [dataSource]="dataSource" matSort aria-label="Elements"> </table> ...... </div>子句中引用另一个Derived Table别名，因为在该级别不能访问该别名。

此外，我觉得您可以使用条件聚合来解决此问题：

FROM

在另一个子查询中使用From（子查询）表

1 个答案: