Question

我有一个相当简单的SQL语句来从几个表中获取一些结果。其中一列是从内联SQL语句生成的。虽然我似乎能够通过此列进行排序，但尝试使用它进行过滤表示该列无效。这是我的代码和错误：

SELECT 
        e.Title as Title,
        -- Get earliest start time and latest end time
        (SELECT TOP 1 l.StartTime FROM Locations l WHERE l.EventID = e.EventID ORDER BY l.StartTime ASC) as EarliestStartTime,
        (SELECT TOP 1 l.EndTime FROM Locations l WHERE l.EventID = e.EventID ORDER BY l.EndTime DESC) as LatestEndTime

    FROM
        Events e
    WHERE
            e.UserID = @UserID
        AND LatestEndTime < DATEADD(DAY, GETDATE(), 1)
    ORDER BY
        EarliestStartTime ASC

错误：

Invalid column name 'LatestEndTime'.

如果删除AND LatestEndTime < DATEADD(DAY, GETDATE(), 1)，则该语句可以正常运行。

Answer 1

您无法在where子句中通过别名引用列。写出来，重复列定义：

WHERE  e.UserID = @UserID
       AND (SELECT TOP 1 l.EndTime FROM Locations l 
            WHERE l.EventID = e.EventID ORDER BY l.EndTime DESC) < 
            DATEADD(DAY, GETDATE(), 1)

或使用子查询命名列：

select  *
from    (
        select  e.Title as Title,
                -- Get earliest start time and latest end time
                (SELECT TOP 1 l.StartTime FROM Locations l
                 WHERE l.EventID = e.EventID ORDER BY l.StartTime ASC)
                 as EarliestStartTime,
                (SELECT TOP 1 l.EndTime FROM Locations l
                 WHERE l.EventID = e.EventID ORDER BY l.EndTime DESC)
                 as LatestEndTime
        from    Events e
        ) as SubQuery
WHERE   UserID = @UserID
        and LatestEndTime < DATEADD(DAY, GETDATE(), 1)

Answer 2

可以尝试使用e.LatestEndTime

看起来您的查询无法确定列LatestEndTime。由于您在查询中使用了Locations l AND Events e，因此它不存在或MySQL只是检查false数据库。

生成的列无效

2 个答案: