作业帮select * from a right join b on a.id=b.id; select * from a join b on a.id=b.id; 有什么区别啊?我怎么感觉第二句完全能代替第一句,那个左右连接,全连接没什么用啊.请哪位高手能讲讲具体的区别!
来源：学生作业帮助网 编辑：作业帮 时间：2024/07/30 04:57:37
x]N@2,k)Z@ @c
EB
UxV6stC/gcb2L={gd8 g>9I%.LRY'8DȢ=|h
8YXjcy͛#Z:hFo:* v3ne.lrƸ `'Zׅ?y?{
Ef.Q[Lڴril6 Kp5ؓ"o Cɰ>J8̉2Q`]C9F5ZEU l i ^4E?ϢyE^vNnQX /iz >4ΔB o
select * from a right join b on a.id=b.id; select * from a join b on a.id=b.id; 有什么区别啊?我怎么感觉第二句完全能代替第一句,那个左右连接,全连接没什么用啊.请哪位高手能讲讲具体的区别!
select * from a right join b on a.id=b.id; select * from a join b on a.id=b.id; 有什么区别啊?
我怎么感觉第二句完全能代替第一句,那个左右连接,全连接没什么用啊.请哪位高手能讲讲具体的区别!
select * from a right join b on a.id=b.id; select * from a join b on a.id=b.id; 有什么区别啊?我怎么感觉第二句完全能代替第一句,那个左右连接,全连接没什么用啊.请哪位高手能讲讲具体的区别!
假如.a id不存在.你第一种方法可以取出来,但是第二哥就会出错.
right的意识就是以第二个表为主,第一个表不存在也会输出
select * from a union select * from b 能详细说下么
select * into b from a where 11
select * from (select a.*,rownum aa from table a ) where aa=10
select *from A where A.a like '%1%'||'%'
Please select a city or zipcode from the drop-down.
Please select a plan from the options to the
select * from book limit ,
insert into a select * from b 和select * into a from b 这两个语句是不是一样的?
select id from (select id from pedigree group by number having count(name)>1)as a; 为啥用as a
select c.*,d* from ( select 图号 from ( SELECT a.*,b.存货编码 FROM 未明图号 as a left OUTER JOIN 存select c.*,d* from ( select 图号 from (SELECT a.*,b.存货编码FROM 未明图号 as a left OUTER JOIN 存货档案 as bON a.图号=b.规
select from 表 和select from [表]有什么不同?
select count(*) from 怎么使用
select count(1) from emp
select * into dept2 from dept
HQL 的语法：select a from a where a=3 or select b from b whereb=2 要怎么写?
select * from tb1 a where =(select min(id2) from tb1 where id1=a.id1)其中的a该如何理解?
帮我看看这个oracle语句,select groupid,parentid,groupname,isleaf,description,sharerankid,statusid,corporationid,staffid,isactual,groupcount,level FROM (SELECT a.*,b.groupcount FROM teabgroup a,(SELECT groupid,count(*) groupcount FROM teabmembe
select * from a,b与select * from a inner join b 的取数方式和执行效率有什么不同,