现在有两个表A_TBL B_TBL
A_TBL 数据如下:id en
1 1
2 0
3 1
4 1B_TBL 数据如下:id aid en
11 1 1
12 2 1
13 3 0
14 3 1
15 4 1
16 2 1
17 5 1(1)
SELECT * FROM A_TBL AS ALEFT JOIN B_TBL AS BON B.aid = A.idAND B.en = 1WHERE A.en = 1(2)
SELECT * FROM A_TBL AS ALEFT JOIN B_TBL AS BON B.aid = A.idAND B.en = 1AND A.en = 1请给我1,2两个查询结果. 并说出原因.
多谢.
A_TBL 数据如下:id en
1 1
2 0
3 1
4 1B_TBL 数据如下:id aid en
11 1 1
12 2 1
13 3 0
14 3 1
15 4 1
16 2 1
17 5 1(1)
SELECT * FROM A_TBL AS ALEFT JOIN B_TBL AS BON B.aid = A.idAND B.en = 1WHERE A.en = 1(2)
SELECT * FROM A_TBL AS ALEFT JOIN B_TBL AS BON B.aid = A.idAND B.en = 1AND A.en = 1请给我1,2两个查询结果. 并说出原因.
多谢.
id en id aid en
----- ----- ----- ------ -----
1 1 11 1 1
3 1 14 3 1
4 1 15 4 1
2、
id en id aid en
----- ----- ------ ------ ------
1 1 11 1 1
2 0 (null) (null) (null)
3 1 14 3 1
4 1 15 4 1 因为1的条件是where,他是在left join后,然后再进行过滤的,所以结果中不会在有en!=1的纪录