Question

我似乎遇到了以下查询的问题。它基本上有效，但我有一个案例，它从mc_WorkoutDetails两次返回一行！

这是原始查询：

ALTER PROCEDURE [dbo].[mc_Workouts_GetActivities]
    @WorkoutID                  bigint
AS
BEGIN
    SET NOCOUNT ON

    SELECT d.ID, a.Description,
            CASE WHEN Reps = 0 THEN NULL ELSE Reps END AS Reps,
            CASE WHEN Sets = 0 THEN NULL ELSE Sets END AS Sets,
            CASE WHEN Minutes = 0 THEN NULL ELSE Minutes END AS Minutes,
            d.Comments, c.Name AS Category, a.CategoryID,
            (CASE WHEN v.ActivityID IS NULL THEN 0 ELSE 1 END) AS HasVideo,
            a.ID AS ActivityID
    FROM mc_WorkoutDetails d
            INNER JOIN mc_Activities a ON d.ActivityID = a.ID
            INNER JOIN mc_Activities_Categories c ON a.CategoryID = c.ID
            LEFT OUTER JOIN mc_TrainerVideos v ON a.ID = v.ActivityID
    WHERE (d.WorkoutID = @WorkoutID)
    ORDER BY SortOrder, a.Description

    RETURN @@ERROR
END

然后我尝试改变：

INNER JOIN mc_Activities a ON d.ActivityID = a.ID
INNER JOIN mc_Activities_Categories c ON a.CategoryID = c.ID

要：

LEFT OUTER JOIN mc_Activities a ON d.ActivityID = a.ID
LEFT OUTER JOIN mc_Activities_Categories c ON a.CategoryID = c.ID

但这似乎没有帮助。我仍然得到重复的行。

有谁能看到发生了什么？

Answer 1

您可以做的是使用组将连接添加回同一个表，以清除重复的行。

所以在FROM mc_WorkoutDetails d：

之后将其添加到您的联接中

inner join (select [columns you want to select], max(id) id
            from mc_WorkoutDetails
            group by [columns you want to select] ) q on q.id = d.id

如果这有意义，请告诉我。基本上你正在做一个独特的并获得最大id，所以你消除了连接中的一行。你必须记住，即使你想要重复，它们也会被淘汰，即使它们被认为是在那里。

完全改变是：

ALTER PROCEDURE [dbo].[mc_Workouts_GetActivities]
@WorkoutID                  bigint
AS
BEGIN
SET NOCOUNT ON

SELECT d.ID, a.Description,
        CASE WHEN Reps = 0 THEN NULL ELSE Reps END AS Reps,
        CASE WHEN Sets = 0 THEN NULL ELSE Sets END AS Sets,
        CASE WHEN Minutes = 0 THEN NULL ELSE Minutes END AS Minutes,
        d.Comments, c.Name AS Category, a.CategoryID,
        (CASE WHEN v.ActivityID IS NULL THEN 0 ELSE 1 END) AS HasVideo,
        a.ID AS ActivityID
FROM mc_WorkoutDetails d
inner join (select Reps, Sets, Comments, Minutes, max(id) id
            from mc_WorkoutDetails
            group by Reps, Sets, Comments, Minutes ) q on q.id = d.id
        INNER JOIN mc_Activities a ON d.ActivityID = a.ID
        INNER JOIN mc_Activities_Categories c ON a.CategoryID = c.ID
        LEFT OUTER JOIN mc_TrainerVideos v ON a.ID = v.ActivityID
WHERE (d.WorkoutID = @WorkoutID)
ORDER BY SortOrder, a.Description

RETURN @@ERROR
END

Answer 2

感谢大家的投入。这里的一般建议是正确的：我在mc_workoutDetails表中有两行引用了mc_Activities表中的同一行。

虽然外键是唯一主键的一部分，但它是一个复合键，因此只要键中的另一列不同，此列就可以包含重复项。

SQL Server查询返回相同的行两次

2 个答案: