SQL Server - 從兩個表和表中獲取數據

Question

請參閱下面的表格和數據 -

DECLARE @test1 TABLE (Ref nvarchar(10) NULL, Dates datetime NULL);
INSERT INTO @test1(Ref, Dates) 
VALUES 
('R1', '2018-10-26'),
('R2', '2018-10-26'),
('R5', null);

DECLARE @test2 TABLE (P_Ref nvarchar(50) null, Name nvarchar(50) null);
INSERT INTO @test2(P_Ref, Name)
VALUES 
('R1', 'N1'),
('R1', 'N2'),
('R2', 'N1'),
('R2', 'N2'),
('R3', 'N1'),
('R3', 'N2'),
('R4', 'N2'),
('R5', 'N3'),
('R6', 'N3'),
('R7', 'N4');

我正在使用表1 @test1 where條件，它的Ref列連接表2 @test2 P_Ref列。 我想要來自兩個表的所有相關數據以及@test2表中的所有匹配Name

我的疑問是 -

select t1.Ref, t2.P_Ref, t2.Name from
@test1 t1
right join @test2 t2
on t1.Ref = t2.P_Ref
where t1.Dates is not null

我得到的輸出 -

   Ref    P_Ref    Name
    R1      R1      N1
    R1      R1      N2
    R2      R2      N1
    R2      R2      N2

我正在尋找下面的輸出 -

   Ref    P_Ref    Name
    R1      R1      N1
    R1      R1      N2
    R2      R2      N1
    R2      R2      N2
    NULL    R3      N1
    NULL    R3      N2
    NULL    R4      N2

有人可以幫助我如何實現這一目標。

提前致謝

Answer 1

請嘗試以下查詢

SELECT t1.Ref, t2.P_Ref, t2.Name
FROM @test1 t1
RIGHT JOIN @test2 t2 ON t1.Ref = t2.P_Ref
WHERE t2.Name IN(
    SELECT DISTINCT t2.Name
    FROM @test1 t1
    JOIN @test2 t2 ON t1.Ref = t2.P_Ref
    WHERE t1.Dates IS NOT NULL
  )

Answer 2

請嘗試以下查詢

select t1.Ref, t2.P_Ref, t2.Name from
@test1 t1 right join @test2 t2
on t1.Ref = t2.P_Ref
where Name in ('N1', 'N2')

Answer 3

如果預期有大量記錄的Dates可能不是NULL那么優化選項將如下所示。

IF OBJECT_ID('tempdb..#ValidRecords') IS NOT NULL
    DROP TABLE #ValidRecords

SELECT DISTINCT t2.[Name]
INTO #ValidRecords
FROM @test1 t1
JOIN @test2 t2 ON t1.Ref = t2.P_Ref
WHERE t1.Dates IS NOT NULL

SELECT Ref,
t2.P_Ref,
t2.[Name]
FROM @test1 t1
RIGHT JOIN @test2 t2 ON t1.Ref = t2.P_Ref
INNER JOIN #ValidRecords vr ON vr.[Name] = t2.[Name]

Answer 4

問題是您的WHERE子句將外部聯接轉換為隱式內部聯接。 要過濾外部表，通常最簡單的方法是將外部表的過濾條件移動到連接條件。

select t1.Ref, t2.P_Ref, t2.Name from
@test1 t1
right join @test2 t2
    on  t1.Ref = t2.P_Ref
    and t1.Dates is not null