Some tips on Basics!

Different types of Tables in Teradata:

Permenant Tables:
1. SET table - Strictly NO duplicate values [By-Default]
2. MULTISET table - Allows Duplicate Values.

Temporary Tables:
1. Global Temporary Table - supports [Compression in table],
when session logged out, Table persists and its record gets
vanished.
2. Volatile Table - When session logged out, TABLE and its
records are not available further.

Derived table: stores the derived result from a subquery.

It uses only spool space, so no table definition, permission needed.

simple query

select * from (select max(sal) from emp) DT (Max_sal)

answer:
derived table(DT) has Max salary and result would be

Max_sal- here subquery result is maintained in derived table
-------
25000

3. derived table auto drops after the query ends