sql 句式问题，求助

Question

select a.*,b.*
from a inner join b on a.djbh=b.djbh and a.je=b.je and a.shl=b.shl不过当你的a中三个列有相同数据时，就要额外处理

Answer 1

table A                                                                               tableB
djbh                je          shl                                 djbh            je         shl    cj
mdj123          10           5                                  mdj123       10         5     1
mdj124           5             1
结果 
djbh         je      shl    cj
mdj123   10      5       1
mdj124    5        1

Answer 2

select a.*,b.cj
from a leftjoin b on a.djbh=b.djbh and a.je=b.je and a.shl=b.shl

Answer 3

IF OBJECT_ID(N'tableA') IS NOT NULL 
DROP TABLE tableAGo
CREATE TABLE tableA(djbh VARCHAR(10),je INT,shl int)
INSERT  INTO tableA
SELECT 'mdj123',10,5 UNION ALL
SELECT  'mdj124',5,1IF OBJECT_ID(N'tableB') IS NOT NULL 
DROP TABLE tableBGo
CREATE TABLE tableB(djbh VARCHAR(10),je INT,shl INT,cj int)
INSERT  INTO tableB
SELECT 'mdj123',10,5,1
-------------------------------------------------查询---------------------------------------------
SELECT a.*,isnull(cast(b.cj as varchar),'') cj FROM tableA a LEFT JOIN tableB b ON a.djbh=b.djbh
 
/*
djbh       je          shl         cj
---------- ----------- ----------- ------------------------------
mdj123     10          5           1
mdj124     5           1           (2 行受影响)
*/

Answer 4

select a.*,isnull(b.cj,'')
from a leftjoin b on a.djbh=b.djbh