Question

我正在试图弄清楚如何在查询中找回真/假值。这是我正在尝试但它无法正常工作。

SELECT TOP 10
    t1.Id as UserId,
    CASE WHEN (t2.UserId = t1.Id AND t2.ItemId = 1) THEN CAST(1 as BIT) ELSE cast(0 as BIT) END as IsFavourite,

    FROM Users t1
    INNER JOIN UserFavorite t2 ON t1.Id = t2.UserId

GROUP BY t1.Id

我得到的错误是：

在选择列表中无效，因为它不包含在聚合函数或GROUP BY子句中。

我知道我需要在小组中分享一些内容才能使其工作，但我不明白。此外，查询已经简化，因为它连接了多个表。

只是为了澄清，收藏夹表基本上有Id，UserId，ItemId。因此，如果有用户和项目的组合，则表示它被收藏。

Answer 1

SELECT TOP 10
t1.Id as UserId,
(CASE WHEN   t2.ItemId = 1 THEN CAST(1 as BIT) ELSE 
cast(0 as BIT) END) as IsFavourite,
FROM Users t1
INNER JOIN UserFavorite t2 ON t1.Id = t2.UserId
GROUP BY t1.Id,t2.ItemId

Answer 2

SELECT TOP 10 *
FROM
(
    SELECT
               t1.Id as UserId
            ,  CASE 
                 WHEN (t2.UserId = t1.Id AND t2.ItemId = 1) 
                 THEN CAST(1 as BIT) 
                 ELSE cast(0 as BIT) END as IsFavourite
            , ROW_NUMBER() OVER (PARTITION BY t1.Id ORDER BY (SELECT NULL)) rn
    FROM Users t1
    INNER JOIN UserFavorite t2 ON t1.Id = t2.UserId
) x
WHERE rn = 1

SQL使用连接和分组选择True或false

2 个答案: