SQLÓï¾ä

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±í1
ÀàÐÍ
1
2
3
4
...
±í2
ÀàÐÍ,ÊýÁ¿
1,200
2,200
3,400
...
±í3
ÀàÐÍ,ÊýÁ¿,ÖØÁ¿
1,200,300
2,400,500
4,200,400
...
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ÀàÐÍ,ÊýÁ¿,ÖØÁ¿
1,200
2,200
3,400
4,200,400
ÔõôдSQL?

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left join

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SQL code:
select a.ÀàÐÍ ,ÊýÁ¿=isnull(b.ÊýÁ¿,c.ÊýÁ¿),c.ÖØÁ¿
from t1 a
left join t2 b on a.ÀàÐÍ=b.ÀàÐÍ
left join t3 c on a.ÀàÐÍ=c.ÀàÐÍ

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ÒýÓÃ

SQL codeselect a.ÀàÐÍ ,ÊýÁ¿=isnull(b.ÊýÁ¿,c.ÊýÁ¿),c.ÖØÁ¿from t1 aleftjoin t2 bon a.ÀàÐÍ=b.ÀàÐÍleftjoin t3 con a.ÀàÐÍ=c.ÀàÐÍ

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ºÃ¾Ã²»¼û
×î½üæɶ

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ÕâÑùдµÃµ½µÄ½á¹ûÊÇ:
1,200,300
2,200,500
3,400
4,200,400
µ«ÊÇÎÒÒªµÄÊÇ:
1,200
2,200
3,400
4,200,400
Ôõô?//

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ÓÐûÓÐÈË°¡.>?

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SQL code:

select a.ÀàÐÍ ,ÊýÁ¿=isnull(b.ÊýÁ¿,c.ÊýÁ¿)
from t1 a
left join t2 b on a.ÀàÐÍ=b.ÀàÐÍ
left join t3 c on a.ÀàÐÍ=c.ÀàÐÍ


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