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±í1
    p  a1, a2 ,a3
    1    1  1  1
    2    2  2  2
    ..
±í2  p  b1, b2, b3
    1  1  1    1
    3  3  3    3
    ..
ÒªÉú³É±í3
    p  a1,a2,a3,b1,b2,b3
    1    1  1  1 1  1  1
    2    2  2  2 0  0  0 
    3    0  0  0 3  3  3
    ..
ÔÚ±í1ºÍ±í2¶¼ÓеļǼҪÔÚ±í3ÖкϳÉÒ»Ìõ¼Ç¼£¬Èç¹ûÖ»ÔÚÒ»¸ö±íÖÐÓеļǼ¾Í¶ÀÁ¢ÏÔʾһÌõ¼Ç¼ÔÚ±í3ÖУ¬Ã»ÓÐÊý¾ÝÒÔ0Ìî¿Õ.

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full join

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FULL JOIN ISNULL

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up

ÒýÓÃ

full join

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SQL code:
select isnull(a.p,b.p) as p,
isnull(a1,0) as a1,
isnull(a2,0) as a2,
isnull(a3,0) as a3,
isnull(b1,0) as b1,
isnull(b2,0) as b2,
isnull(b3,0) as b3
from a
full join b on a.p=b.p

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ÒýÓÃ

±í1
    p  a1, a2 ,a3
    1    1  1  1
    2    2  2  2
    ..
±í2  p