Combining 2 select statements - sql

Question

I have 2 select statements having a common column POL.SP_NUM which I wish to combine. I am new to SQL and haven't the slightest clue how to go about with the same.
Query 1:
select POL.SP_NUM POL#
, POL.ASSET_NUM COV#
, count(distinct(POLX.ATTRIB_06)) COUNT_ADDENDA
, count(distinct(POLX.ATTRIB_07)) COUNT_CERT
, sum(POL.QTY) SI
from S_ASSET POL
, S_ASSET_X POLX
Where POL.ROW_ID = POLX.ROW_ID
and POL.SP_NUM in ('000','111','222')
group by
POL.SP_NUM
, POL.ASSET_NUM
Query 1 output:
POL# COV# COUNT_ADDENDA COUNT_CERT SI
000 856 2 0 1000
111 123 0 0 500
222 567 0 1 2000
Query 2:
select POL#, sum(DOCI)
from (
select POL.SP_NUM POL#, sum(Q.AMT + POL.AMT) DOCI
from S_ASSET POL
, S_QUOTE_ITEM Q
where POL.X_QUOTE_ID = Q.ROW_ID
and POL.SP_NUM in ('000','111','222')
group by POL.SP_NUM
UNION ALL
select POL.SP_NUM POL#, sum(QXM.AMT) DOCI
from S_ASSET POL
, S_QUOTE_ITEM Q
, S_QUOTE_ITEM_XM QXM
where POL.X_QUOTE_ID = Q.ROW_ID
and Q.ROW_ID = QXM.PAR_ROW_ID
and POL.SP_NUM in ('000','111','222')
group by POL.SP_NUM
)
group by POL#
Query 2 output:
POL# sum(DOCI)
000 90
111 0
222 10
Desired output:
POL# COV# COUNT_ADDENDA COUNT_CERT SI sum(DOCI)
000 856 2 0 1000 90
111 123 0 0 500 0
222 567 0 1 2000 10
If there is a better way to code this? Suggestions are welcome.

Answer 1

This is no answer to the question, but an answer to the request to explain the join types made in the comments setion.
INNER JOIN (or short: JOIN)
select * from t1 join t2 on t1.colx = t2.coly
only gives you matches. This is the most common join. You could replace the ON clause with a USING clause in case the columns in the ON clause have the same names in the tables. Sometimes usefull to quickly write a query, but I would generally not recommend USING.
LEFT OUTER JOIN (or short: LEFT JOIN)
select * from t1 left join t2 on t1.colx = t2.coly
gives you all t1 records, no matter whether they have a math in t2. So when there is a match or more for a t1 record, then you join these just as wih an inner join, but when a t1 record has no match in t2 then you get the t1 record along with an empty t2 record (all columns are NULL, even the columns you used in the ON clause, which is t2.coly in above example). In other words: you get all records you'd get with an inner join plus all t1 records that have no match in t2.
You can also use a RIGHT JOIN so you'd keep t2 records when there is no t1 match:
select * from t1 right join t2 on t1.colx = t2.coly
but this is regarded less readable by many people, so better don't use right outer joins, but simply swap tables then:
select * from t2 left join t1 on t1.colx = t2.coly
FULL OUTER JOIN (or short: FULL JOIN)
select * from t1 full outer join t2 on t1.colx = t2.coly
this gives you all records from both t1 and t2, no matter whether they have a match in the other table or not. Again: You get all records you'd get with an inner join plus all t1 with no t2 match plus all t2 with no t1 match.
When having several full outer joins the USING clause can come in handy:
select product, sum(p1.amount), sum(p2.amount), sum(p3.amount)
from p1
full outer join p2 using (product)
full outer join p3 using (product);
CROSS JOIN
A cross join joins a table without any criteria, so as to combine each of its records with each of the records already present. This is used to get all combinations and usually followed by a left outer join:
select products.product_id, regions.region_id, count(*)
from products
cross join regions
left join sales on sales.product_id = products.product_id
and sales.region_id = regions.region_id
group by products.product_id, regions.region_id
order by products.product_id, regions.region_id;
This gives you all possible combinations of products and regions and counts the sales therein. So you get a result record even for product / region combinations where nothing was sold (i.e. no entry in table sales).
NATURAL JOIN
looks at common column names to magically join tables. My simple advice: never use this join type.
ANTI JOIN
This is not a join type actually, but a usage of a join, namely an outer join. Here you want to get all records from a table except the matches. You achieve this by outer-joining the tables and then removing matches in the where clause.
select t1.*
from t1
left join t2 on t1.colx = t2.coly
where t2.coly is null;
This looks queer, because we have EXISTS (and IN) to check for existence:
select *
from t1
where not exists (select * from t2 where t2.coly = t1.colx);
So why would one obfuscate things and use the anti join pattern instead? It is a trick used on weak DBMS. When a DBMS is written, joins are the most important thing and the developers of the DBMS put all their effort into making them fast. They may neglect EXISTS and IN at first and only later care about their performance. So it may help then to use a join technique (the anti join) instead. My recommendation: Only use the anti join pattern when running into performance issues with a straight-forward query. So far I've never had to use anti joins it in more than twenty years. (It's good to have that option though. And it's good to know about them, so as to not be confused when stumbling upon such query some time :-)

Answer 2

You can join the queries:
select *
from (your query 1 here) query1
join (your query 2 here) query2 on query2.pol# = query1.pol#;
The same with WITH clauses:
with query1 as (your query 1 here),
query2 as (your query 2 here)
select *
from query1
join query2 on query2.pol# = query1.pol#;