Referring to other SQL scripts from a SQL script? - sql

Question

I'm currently converting MS access queries to SQL queries and noticed that in the access query it appears to be joining another query to other tables. So I looked around and it seems like that query pretty much makes the query look cleaner without needing to have all sorts of subqueries in the same script
Something like
FROM [query name] INNER JOIN [some other table]
Is there something like this in SQL?

Answer 1

You are probably looking for VIEWS.
A view is basically a stored version of a SELECT query. It allows you to reference the result set without rewriting the query every time.

Answer 2

You can create a VIEW as a query, then reference the view in another query.
CREATE VIEW <viewname> AS <SELECT STATEMENT>
then
SELECT * FROM <viewname> INNER JOIN <other table>

Answer 3

Yes. They are called views.
You can create a view like
CREATE VIEW vw_some_query AS
SELECT * FROM
table_a LEFT INNER JOIN table_b ON table_a.id = table_b.id2
then you can write a select like:
SELECT * FROM vw_some_query LEFT INNER JOIN table_c ON vw_some_query.id = table_c.id3

Answer 4

Is there something like this in SQL?
Yes. In SQL you would probably use the WITH clause:
WITH someData AS
(
select a.col1, b.col2
from tableA a join tableB b
on (a.someKey = b.someKey)
),
...
select data1.col1, data1.col2, data2.col3
from someData data1 join tableC data2
on (data1.col1 = data2.anotherKey)
where ...
Views are ok too, but another db object to keep track of, and if using a materialized view, need to worry about refreshing snapshot table, etc. My suggestion is to use WITH along with plenty of comments where possible.
EDIT: If you find yourself asking the same question of the db over and over, then a view (or mat view) would be more appropriate. But otherwise, keep logic in the query.