|
|
Archives of the TeradataForum
Message Posted: Thu, 21 May 2009 @ 14:47:37 GMT
Subj: | | Column Order in Derived Table |
|
From: | | Goli, Srikanth |
Hi -
Does Teradata optimizer need the select columns in a subquery to create a derived table to be in a specific order?
Assume the following -
SEL ....
FROM A
Join (Sel
From B
Where ..
)C
ON A.Col1 = B.Col1
Does it use the first column in the derived table B as the PI OR does the optimizer understand that regardless of location of B.Col1,
that needs to be driver for distribution / hashing? I understand that with standalone "Create Tables As", this is a factor and that first column
either be the PI column, or PI be explicitly specified. But with a derived table, where optimizer has access to statistics and query, does it
still need the user specify the order?
Thanks.
| |