cannot create a single result set oracle joins or subqueries - sql

Question

I have three basic queries that are related to each other and I need a single result set to return.
Simplified:
Query1 (possible return not a show stopper return null):
SELECT * FROM monkey WHERE monkey.ENDDATE IS NULL AND monkey.TEMPLATEID = 1
Query2 (possible return not a show stopper return null):
SELECT * FROM banana WHERE banana.ENDDATE IS NULL AND banana.TEMPLATEID = 1
Query3 (must return something):
SELECT * FROM tree WHERE tree.TEMPLATEID = 1
Query 1 and 2 may or may not return a value (come back null).
The third one will need to return a result (or not) IF the third query returns something I and query 1 or 2 fail I still want to return something.
I can’t do an outer join with 2 queries, because oracle won’t let me the error said… a.b (+) = b.b and a.c(+) = c.c is not allowed instead turn b+c into a view.
I think I understand the logical reason, never-the-less I need to return query 3 and maybe query 1, 2 or 1 and 2 along with 3 as a single result set.
I hope this makes sense.

Answer 1

You seem to be hitting ORA-01417. Using made up tables and data as you haven't provided any, or the join conditions, I can get the same effect by trying to outer join monkey to both tree and banana - in a completely contrived way, of course:
with banana as (select 'yellow' as colour, 1 as template_id, null as enddate
from dual),
monkey as (select 'capuchin' as monkeytype, 1 as template_id, null as enddate
from dual),
tree as (select 'tropical' as treetype, 1 as template_id from dual)
select t.treetype, b.colour, m.monkeytype
from tree t, banana b, monkey m
where t.template_id = 1
and b.template_id (+) = t.template_id
and b.enddate (+) is null
and m.template_id (+) = t.template_id
and m.enddate (+) is null
and m.template_id (+) = b.template_id;
Error at Command Line:10 Column:22
Error report:
SQL Error: ORA-01417: a table may be outer joined to at most one other table
01417. 00000 - "a table may be outer joined to at most one other table"
*Cause: a.b (+) = b.b and a.c (+) = c.c is not allowed
*Action: Check that this is really what you want, then join b and c first
in a view.
if you use the 'new' (since 9i, I think) ANSI join syntax, rather the Oracle-specific (+) notation, you can do more:
with banana as (select 'yellow' as colour, 1 as template_id, null as enddate
from dual),
monkey as (select 'capuchin' as monkeytype, 1 as template_id, null as enddate
from dual),
tree as (select 'tropical' as treetype, 1 as template_id from dual)
select t.treetype, b.colour, m.monkeytype
from tree t
left join banana b on b.template_id = t.template_id
and b.enddate is null
left join monkey m on m.template_id = t.template_id
and m.enddate is null
and m.template_id = b.template_id
where t.template_id = 1;
TREETYPE COLOUR MONKEYTYPE
-------- ------ ----------
tropical yellow capuchin
See the documentation for some of the restrictions on (+); Oracle recommend using the ANSI version, though they seem to use their own most of the time in examples in the documentation.

Answer 2

I suspect, that the tables, "monkey", "banana", and "tree" all have different column types, otherwise you can easily obtain what you want using a "UNION" or "UNION ALL" operator.
Also since you haven't shared the table defn. of these tables, I don't know if you have any foreign keys to join these tables or not. SO I am assuming they are completely unrelated.
So with these 2 assumptions....
Here's another way, of returning combined resultsets from different queries.
SELECT CURSOR(QRY1), CURSOR(QRY2), CURSOR(QRY3) FROM DUAL;
This will give you all three result-sets in one query. But each result-set is a ref-cursor which you'll have to navigate in your application.
If using java, the java type of each of the 3 columns, is a ResultSet, which you'll have to navigate, to get individual query results.
e.g.
String qry1= "SELECT * FROM monkey WHERE monkey.ENDDATE IS NULL";
String qry2 = " SELECT * FROM banana WHERE banana.ENDDATE IS NULL AND banana.TEMPLATEID = 1";
String qry3= "SELECT * FROM tree WHERE tree.ENDDATE IS NULL AND tree.TEMPLATEID = 1";
String qry = "SELECT CURSOR("+qry1+"), CURSOR("+qry2+"), CURSOR("+qry3+") FROM DUAL";
ResultSet rs = conn.createStatement().executeQuery(qry);
if(rs.next()) { //no while loop necessary, as we are expecting only one row
ResultSet rs1 = (ResultSet) rs.getObject(1);
ResultSet rs2 = (ResultSet) rs.getObject(2);
ResultSet rs3 = (ResultSet) rs.getObject(3);
while(rs1.next()) {
// retrive results of qry1
}
// same for rs2 and rs3
}
Hope that helped.