談談oracle里的join、left join、right join

create table l as
select 'left_1' as str,'1' as v from dual union all
select 'left_2' ,'2' as v from dual union all
select 'left_3' ,'3' as v from dual union all
select 'left_4' ,'4' as v from dual ;

create table r as
select 'right_3' as str,'3' as v, 1  as status from dual union all
select 'right_4' as str,'4' as v, 0  as status from dual union all
select 'right_5' as str,'5' as v, 0  as status from dual union all
select 'right_6' as str,'6' as v, 0  as status from dual ;

select * from l; --where l.v not in (select r.v from r )

select * from r

--1. inner join 返回兩表相匹配的數據  即 交集
select l.str as left_str,r.str as right_str from l
inner join r on l.v=r.v
order by 1,2;

select l.str as left_str,r.str rigth_str from l,r
where l.v=r.v
order by 1,2;

--2.left join  左表為主表，左表返回全部數據，右表只返回與左表相匹配的數據
select l.str as left_str,r.str right_str from l
left join r on l.v=r.v
order by 1,2;

select l.str as left_str,r.str as right_str from l,r
where l.v=r.v(+)
order by 1,2;

select l.str as left_str,r.str as right_str from l,r
where l.v=r.v
order by 1,2;
 
--3.right join 右表為主表，左表只返回與右表相匹配的數據
select l.str as left_str,r.str as right_str from l
right join r on l.v=r.v
order by 1,2;

select l.str as left_str,r.str right_str from l,r
where l.v(+)=r.v
order by 1,2;

--4. 左右表均返回全部的數據，但是只有相匹配的數據顯示在一行，非匹配的數據只顯示一個表的數據
select l.str as left_str,r.str as right_str from l
full join r on r.v=l.v
order by 1,2;