SQL连接查询AND和WHERE的不同

如下两张表：
表A 表B
--- ---
F F
--- ---
A A
B B
C F
D G
E H
--- ---

WHERE:

SELECT A.F AS FA, dbo.B.F AS FB
FROM dbo.A LEFT OUTER JOIN dbo.B ON dbo.A.F = dbo.B.F
WHERE A.F = 'A'
-----------
FA FB
-----------
A A
-----------

AND:

SELECT A.F AS FA, dbo.B.F AS FB
FROM dbo.A LEFT OUTER JOIN dbo.B ON dbo.A.F = dbo.B.F
AND A.F = 'A'
------------
FA FB
------------
A A
B null
C null
D null
E null
------------

可以看出使用 WHERE 条件会筛选连接查询的结果，但不影响返回的右表字段值；
使用 AND 不会对结果进行筛选，结果一定是包含了所有的左表记录，但是会影响
返回的右表字段值，如果 ON 后面的逻辑判断返回 true 显示右表值，为 false 则显示 null。

SELECT A.F AS FA, dbo.B.F AS FB
FROM dbo.A LEFT OUTER JOIN dbo.B ON dbo.A.F = dbo.B.F AND 1 = 1

FA FB
------------
A A
B B
C null
D null
E null
------------

SELECT A.F AS FA, dbo.B.F AS FB
FROM dbo.A LEFT OUTER JOIN dbo.B ON dbo.A.F = dbo.B.F AND 1 = 2

FA FB
------------
A null
B null
C null
D null
E null
------------

如果是 INNER JOIN， WHERE 和 AND 效果相同。

SELECT A.F AS FA, dbo.B.F AS FB
FROM dbo.A INNER JOIN dbo.B ON dbo.A.F = dbo.B.F
WHERE A.F = 'A' / AND A.F = 'A'

-----------
FA FB
-----------
A A
-----------