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--------------------------------------------
1.left join
sqlÓï¾äÈçÏÂ:
select * from A
left join B
on A.aID = B.bID
½á¹ûÈçÏÂ:
aID¡¡¡¡¡¡¡¡¡¡aNum¡¡¡¡¡¡¡¡¡¡bID¡¡¡¡¡¡¡¡¡¡bName
1¡¡¡¡¡¡¡¡¡¡a20050111¡¡¡¡¡¡¡¡1¡¡¡¡¡¡¡¡¡¡2006032401
2¡¡¡¡¡¡¡¡¡¡a20050112¡¡¡¡¡¡¡¡2¡¡¡¡¡¡¡¡¡¡2006032402
3¡¡¡¡¡¡¡¡¡¡a20050113¡¡¡¡¡¡¡¡3¡¡¡¡¡¡¡¡¡¡2006032403
4¡¡¡¡¡¡¡¡¡¡a20050114¡¡¡¡¡¡¡¡4¡¡¡¡¡¡¡¡¡¡2006032404
5¡¡¡¡¡¡¡¡¡¡a20050115¡¡¡¡¡¡¡¡NULL¡¡¡¡¡¡¡¡¡¡NULL
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left joinÊÇÒÔA±íµÄ¼Ç¼Ϊ»ù´¡µÄ,A¿ÉÒÔ¿´³É×ó±í,B¿ÉÒÔ¿´³ÉÓÒ±í,left joinÊÇÒÔ×ó±íΪ׼µÄ.
»»¾ä»°Ëµ,×ó±í(A)µÄ¼Ç¼½«»áÈ«²¿±íʾ³öÀ´,¶øÓÒ±í(B)Ö»»áÏÔʾ·ûºÏËÑË÷Ìõ¼þµÄ¼Ç¼(Àý×ÓÖÐΪ: A.aID = B.bID).
B±í¼Ç¼²»×ãµÄµØ·½¾ùΪNULL.
--------------------------------------------
2.right join
sqlÓï¾äÈçÏÂ:
select * from A
right join B
on A.aID = B.bID
½á¹ûÈçÏÂ:
aID¡¡¡¡¡¡¡¡¡¡aNum¡¡¡¡¡¡¡¡¡¡bID¡¡¡¡¡¡¡¡¡¡bName
1¡¡¡¡¡¡¡¡¡¡a20050111¡¡¡¡¡¡¡¡1¡¡¡¡¡¡¡¡¡¡2006032401
2¡¡¡¡¡¡¡¡¡¡a20050112¡¡¡¡¡¡¡¡2¡¡¡¡¡¡¡¡¡¡2006032402
3¡¡¡¡¡¡¡¡¡¡a20050113¡¡¡¡¡¡¡¡3¡¡¡¡¡¡¡¡¡¡2006032403
4¡¡¡¡¡¡¡¡¡¡a20050114¡¡¡¡¡¡¡¡4¡¡¡¡¡¡¡¡¡¡2006032404
NULL¡¡¡¡¡¡¡¡¡¡NULL¡¡¡¡¡¡¡¡¡¡8¡¡¡¡¡¡¡¡¡¡2006032408
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½á¹û˵Ã÷:
×Ðϸ¹Û²ìÒ»ÏÂ,¾Í»á·¢ÏÖ,ºÍleft joinµÄ½á¹û¸ÕºÃÏà·´,Õâ´ÎÊÇÒÔÓÒ±í(B)Ϊ»ù´¡µÄ,A±í²»×ãµÄµØ·½ÓÃNULLÌî³ä.
--------------------------------------------
3.inner join
sqlÓï¾äÈçÏÂ:
select * from A
innerjoin B
on A.aID = B.bID
½á¹ûÈçÏÂ:
aID¡¡¡¡¡¡¡¡¡¡aNum¡¡¡¡¡¡¡¡¡¡bID¡¡¡¡¡¡¡¡¡¡bName
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#include "iostream.h"
#include "stdio.h"
#import "C:\program files\common files\system\ado\msado15.dll" no_namespace rename("EOF","adoEOF")
int main(int argc, char* argv[])
{
   ::CoInitialize(NULL);
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CREATE proc sqlToMultiExcelFile
@sqlstr nvarchar(4000), --²éѯÓï¾ä,Èç¹û²éѯÓï¾äÖÐʹÓÃÁËorder by ,Çë¼ÓÉÏtop 100 percent
@primaryKey varchar(100),--·ÖÒ³Ö÷¼ü×Ö¶Î
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    select getdate()
2. dateadd ÔÚÏòÖ¸¶¨ÈÕÆÚ¼ÓÉÏÒ»¶Îʱ¼äµÄ»ù´¡ÉÏ£¬·µ»ØÐ嵀 datetime Öµ
   ÀýÈ磺ÏòÈÕÆÚ¼ÓÉÏ2Ìì
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