mysql²Ù×÷ Left join , Right Join, Inner Join
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Table A
aid adate
1 a1
2 a2
3 a3
TableB
bid bdate
1 b1
2 b2
4 b4
Á½¸ö±ía,bÏàÁ¬½Ó,Ҫȡ³öidÏàͬµÄ×Ö¶Î
select * from a inner join
b on a.aid = b.bidÕâÊǽöÈ¡³öÆ¥ÅäµÄÊý¾Ý.
´ËʱµÄÈ¡³öµÄÊÇ:
1 a1 b1
2 a2 b2
ÄÇôleft join Ö¸:
select * from a left join
b on
a.aid = b.bid
È¡³öa±íËùÓÐÊý¾Ý,ÄÃbµÄÊý¾ÝÓëa±È½Ï,ÏàͬµÄÈ¡³ö,²»Í¬µÄbÈ¡¿Õֵȡ³ö
´ËʱµÄÈ¡³öµÄÊÇ:
1 a1 b1
2 a2 b2
3 a3 ¿Õ×Ö·û
ͬÑùµÄÒ²ÓÐright join
select * from a right join
b on
a.aid = b.bid
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´ËʱµÄÈ¡³öµÄÊÇ:
1 a1 b1
2 a2 b2
4 ¿Õ×Ö·û b4
×¢:
¶¼ÊÇÔÚonµÄÌõ¼þÏÂ
¶þ. left join/right join/inner join²Ù×÷ÑÝʾ
±íA¼Ç¼ÈçÏ£º
aID aNum
1 a20050111
2 a20050112
3 a20050113
4 a20050114
5 a20050115
±íB¼Ç¼ÈçÏÂ:
bID bName
1 2006032401
2 2006032402
3 2006032403
4 2006032404
8 2006032408
ʵÑéÈçÏÂ:
1. left join
sqlÓï¾äÈçÏÂ:
SELECT
*
from
A
LEFT
JOIN
B
ON
A.aID
=
B.bID
½á¹ûÈçÏÂ:
aID aNum &
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