Re: Select statement in from clause

Proffesional newbie wrote:

> Hi i found the next select statement and i was wondering what this
> select statement in the from clause does ?
> It is the first time i see this.

Basically it is a view. Consider this view: CREATE VIEW foo AS SELECT * FROM table2 WHERE col1 < SYSDATE

We select from this view:
SELECT
  *
FROM foo

Replace the view name with its select and you get: SELECT
  *
FROM (SELECT * FROM table2 WHERE col1 < SYSDATE)

There is very little difference between SQL 1 and SQL 2. In 2 we simply substituted the name of the view with the actual SELECT statement for that view. Which is exactly what the database engine does with SQL 1.

--
Billy