Reuse a piece of code in SQL?

Question

I have a big SQL. And inside it, there is a piece of sub-query appear twice. So rather than writing the sub-query twice in the big SQL, I hope to reuse the sub-query in the "big SQL", i.e., is it possible that I only write it when it first appears, and when it appears again in the other places in the same big SQL, I only need to refer to it rather than re-write the whole sub-query once again? Hope the above does not confuse you. Thanks!

Answer 1

This is a nonsensical example of the WITH clause but should give you an idea of the syntax. I've created 2 subqueries (my_tabs, my_objs). Once they're given a name, they can be used in a statement anywhere where you would use a table (or subquery). You can use them multiple times, but they can't be correlated subqueries. They have to be 'stand alone'.
WITH
my_tabs AS (SELECT table_name FROM user_tables)
,my_objs AS (SELECT object_name FROM user_objects)
SELECT *
FROM my_tabs
    ,my_objs
WHERE my_tabs.table_name = my_objs.object_name
;