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--½¨Á¢²âÊÔÊý¾Ý
create table a(id number);
create table b(id number);
insert into a values(1);
insert into a values(2);
insert into a values(3);
insert into b values(1);
insert into b values(2);
insert into b values(4);
commit;
--×ó:
--Ö÷Á÷Êý¾Ý¿âͨÓõķ½·¨
select * from a left join b on a.id=b.id;
--OracleÌØÓеķ½·¨
select * from a, b where a.id=b.id(+);
ID ID
---------- ----------
1 1
2 2
3
--ÓÒ£º
--Ö÷Á÷Êý¾Ý¿âͨÓõķ½·¨
select * from a right join b on a.id=b.id;
--OracleÌØÓеķ½·¨
select * from a, b where a.id(+)=b.id;
ID ID
---------- ----------
1 1
2 2
4
--ÄÚ
--Ö÷Á÷Êý¾Ý¿âͨÓõķ½·¨
select * from a join b on a.id=b.id;
--where¹ØÁª
select * from a, b where a.id=b.id;
ID ID
---------- ----------
1 1
2 2
--È«Íâ
--Ö÷Á÷Êý¾Ý¿âͨÓõķ½·¨
select * from a full join b on a.id=b.id;
--OracleÌØÓеķ½·¨
select *
from a, b
where a.id = b.id(+)
union
select *
from a, b
where a.id(+) = b.id;
ID ID
---------- ----------
1 1
2 2
3
4
--ÍêÈ«£¬Ò²½Ð½»²æÁ¬½Ó»òÕߵѿ¨¶û»ý
--Ö÷Á÷Êý¾Ý¿âͨÓõķ½·¨
select * from a,b;
--»òÕß
select * from a cross join b;
ID ID
---------- ----------
1 1
1 2
1 4
2 1
2 2
2 4
3 1
3 2
3 4
Á¬½ÓÎÞ·ÇÊÇÕ⼸¸ö
--ÄÚÁ¬½ÓºÍwhereÏàͬ
inner join
--×óÏòÍâÁ¬½Ó£¬·µ»Ø×ó±ß±íËùÓзûºÏÌõ¼þµÄ
left join
--ÓÒÏòÍâÁ¬½Ó£¬·µ»ØÓұ߱íËùÓзûºÏÌõ¼þµÄ
right join
--ÍêÕûÍⲿÁ¬½Ó£¬×óÏòÍâÁ¬½ÓºÍÓÒÏòÍâÁ¬½ÓµÄºÏ¼¯
full join
--½»²æÁ¬½Ó£¬Ò²³ÆµÑ¿¨¶ù»ý¡£·µ»Ø×ó±íÖеÄÿһÐÐÓëÓÒ±íÖÐËùÓÐÐеÄ×éºÏ
cross join
--²¹³ä£º
--×óÏòÍâÁ¬½Ó£¬·µ»Ø×ó±ß±íËùÓзûºÏÌõ¼þµÄ£¬
--×¢ÒâÕâÀïûÓеڶþ¸ö¼ÓºÅ£¬»áÖ±½Ó¹ýÂ˵ôÊý¾Ý£¬Ö»ÏÔʾ·ûºÏÌõ¼þµÄ¼Ç¼
select *
from a, b
where a.id = b.id(+)
and b.id = 2;
ID ID
---------- ----------
2 2
--×óÏòÍâÁ¬½Ó£¬·µ»Ø×ó±ß±íËùÓзûºÏÌõ¼þµÄ
--×¢ÒâwhereÉϵڶþ¸ö¼ÓºÅ£¬ËüµÄ×÷ÓÃÊÇÐÞ¸ÄÓұ߱í¼Ç¼µÄÏÔʾ£¬ÀýÈçÈç¹ûb.id(+) = 2£¬ÏÔʾΪ2£¬·ñÔòÏÔʾnull
select *
from a, b
where a.id = b.id(+)
and b.id(+) = 2;
ID ID
---------- --


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