About the more child query, one of them is empty, the all data all have no, how to solve the problem of the

Select * from
(select f1 from t1 where... ) a1,
(select f1 from t1 where... ) a2,
The from t2 (select f1 where... A3,
.

If there is no record of a1, even other sub queries, the main query didn't count, I think whether or not the subquery is there a number, as long as there is record, other sub queries can get, how to solve?

CodePudding user response:

The building Lord gives some test data, and your expected results, didn't see you want to achieve what kind of effect;

CodePudding user response:

The need to make sure that a piece of the main table, it means that there must be a data, the other may not, associated with outside connection line Anderson, d=b.i d (+) and Anderson, d=c.i d (+)
If can not, can use multiple union two two imprison LianZha it,

CodePudding user response:

Table t1
F1 rq
10 the 2016-10-13
F2 rq
20 2016-10-11

Select a1. F1, a1. F1 - a2. F1 from
(select f1 from t1 where rq='2016-10-13') a1,
(select f1 from t1 where rq='2016-10-12') a2

The 12th day no data, as a result, the main query didn't record
I don't think to realize even 12 data, but still can get data from 13, namely get 10

CodePudding user response:

Ahking

reference 3 floor response:

table t1
F1 rq
10 the 2016-10-13
F2 rq
20 2016-10-11

Select a1. F1, a1. F1 - a2. F1 from
(select f1 from t1 where rq='2016-10-13') a1,
(select f1 from t1 where rq='2016-10-12') a2

The 12th day no data, as a result, the main query didn't record
I don't think to realize even 12 data, but still can get data from 13, namely get 10

With a LEFT JOIN implementation

SQL> The select e. * from emp where e e.e mpno=7369;

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
17-7369 SMITH at 7902-80, 800 in December 20

SQL> The select e. * from emp where e e.e mpno=7970;

Not selected row

SQL> The select e1. * from (select e. * from emp where e e.e mpno=7369) e1 left join
E. 2 (the select * from emp where e e.e mpno=7970) e2 on e1, empno=e2. Empno;

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
17-7369 SMITH at 7902-80, 800 in December 20

CodePudding user response:

Outer join

 with t1 as 
(select 10 f1, '2016-10-13' rq from dual 
Union all 
Select 20 f1, '2016-10-11' rq from dual 
) 
Select a1. F1, a1. F1 - a2. F1 from 
(select f1 from t1 where rq='2016-10-13') a1 
Full join 
(select f1 from t1 where rq='2016-10-12') a2 
On 1=1 

CodePudding user response:

Suggested that baidu oracle + left connect (connection),
With reference to your SQL, upstairs again understand left after connection
Please refer to the
http://bbs.csdn.net/topics/390152319

CodePudding user response:

5/f, external connection is ok

CodePudding user response:

The select f1 from t1 where.. Union select f2 from t2 where... Union select f3 from t3 where..

CodePudding user response:

reference 1st floor wmxcn2000 response:

the building Lord gives some test data, and your expected results, didn't see you want to achieve what kind of effect;