連接條款中的條件和條款

Question

之間的區別我想知道兩個SELECT語句之間的差異（可視化）是最好的。

SELECT P.* and X.* 
FROM Table1 P 
LEFT OUTER JOIN 
    Table2 X ON 
    and p.B=x.B 
and p.C=x.C 
and p.F=x.F 
and p.D=x.D 

WHERE X.F= 1 and X.E=4 

和

SELECT P.* and X.* 
FROM Table1 P 
LEFT OUTER JOIN 
    (SELECT * FROM Table2 WHERE X.F= 1 and X.E =4) X 
    and p.B=x.B 
and p.C=x.C 
and p.F=x.F 
and p.D=x.D 

他們不返回相同的行數。可以說，表1有5000行，表2也有5000行。第一條select join語句返回〜40000行（特定於我的查詢），然後應用where子句時，它返回大約2000行。

第二個select join語句返回5000行（原始數字）。這是我想要的數字。

但我似乎無法理解爲什麼會發生這種情況。我的知識和可視化聯接有點弱。

示例數據：請更改臨時表的名稱，它們是相同的。此外，我不能提供適當的列名，但已經編輯我的代碼來指示columsn我想匹配 這裏是表1：

SELECT * INTO #tmp_GridResults_1 
FROM (
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'1' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'1' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'1' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'1' AS [E], N'2' AS [F]) t; 
SELECT [ID], [B], [C], [D], [E], [F] 
FROM #tmp_GridResults_1 

DROP TABLE #tmp_GridResults_1 
GO 

下面是表2： ------------ ---＃tmp_GridResults_1 ---------------

SELECT * INTO #tmp_GridResults_1 
FROM (
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'0' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'0' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'0' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'0' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'0' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'0' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'0' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'0' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'1' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'1' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'1' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'1' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'1' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'1' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'1' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'2' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'2' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'2' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'2' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'2' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'2' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'2' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'2' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'2' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'2' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'2' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'2' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'3' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'3' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'3' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'3' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'3' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'3' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'3' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'3' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'3' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'3' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'3' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'3' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'4' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'4' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'4' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'4' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'4' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'4' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'4' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'4' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'4' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'4' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'4' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'4' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'98' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'98' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'-1' AS [D], N'98' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'-1' AS [D], N'98' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'98' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'98' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'0' AS [D], N'98' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'0' AS [D], N'98' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'98' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'98' AS [E], N'1' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'1' AS [C], N'1' AS [D], N'98' AS [E], N'2' AS [F] UNION ALL 
SELECT N'0' AS [ID], N'P' AS [B], N'2' AS [C], N'1' AS [D], N'98' AS [E], N'2' AS [F]) t; 
SELECT [ID], [B], [C], [D], [E], [F] 
FROM #tmp_GridResults_1 

DROP TABLE #tmp_GridResults_1 
GO 

Answer 1

如果你把過濾條件在WHERE子句中，而標準規定針對的「外」表條件連接，你可以有效地將外連接變成一個內連接。針對外部連接表的篩選條件屬於連接，而不屬於where。

此版本產生多少行？

SELECT P.*, X.* 
FROM Table1 P 
LEFT OUTER JOIN Table2 X 
    on P.Id = X.id 
    and P.name = X.name 
    and P.age = X.age 
    AND X.bar = 1 
    and X.name ='value'; 

從理論上講，這應該產生> =您的第一條語句的行數和列=在你的第二個的數量。

如果你想與您現有的結果進行比較這一點，你可以這樣做：

SELECT P.*, X.* 
FROM Table1 P 
LEFT OUTER JOIN Table2 X 
    on P.Id = X.id 
    and P.name = X.name 
    and P.age = X.age 
    AND X.bar = 1 
    and X.name ='value' 
EXCEPT 
SELECT P.* and X.* 
FROM Table1 P 
LEFT OUTER JOIN 
    (SELECT * FROM Table2 WHERE X.bar = 1 and X.name ='value') X 
    on P.Id = X.id 
    and P.name = X.name 
    and P.age = X.age; 

如果你沒有得到結果，它們是相同的。你也可以做相反的方式：

SELECT P.*, X.* 
FROM Table1 P 
LEFT OUTER JOIN Table2 X 
    on P.Id = X.id 
    and P.name = X.name 
    and P.age = X.age 
    AND X.bar = 1 
    and X.name ='value' 
INTERSECT 
SELECT P.* and X.* 
FROM Table1 P 
LEFT OUTER JOIN 
    (SELECT * FROM Table2 WHERE X.bar = 1 and X.name ='value') X 
    on P.Id = X.id 
    and P.name = X.name 
    and P.age = X.age; 

如果你得到5000行（或任何確切的行數是由本身後者查詢），那麼結果集是相同的。