Archives of the TeradataForum
Message Posted: Fri, 28 Aug 2009 @ 10:21:18 GMT
| Subj: | | Re: Parsing of SQL in teradata |
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| From: | | Dieter Noeth |
Rahul Shashidhar Phadnis wrote:
| | My question was exactly that when I write a sql (before I actually do the explain),do I need to worry about the order of where and join
clauses ? Or anyhow I put it the teradata v2r6 optimizer is 'smart' enough to give me a low cost way of executing the same? | |
Pre-TD12 the optimizer will evaluate WHERE-conditions on a single table based on the order of conditions.
The bad thing: there is no fixed order, it might choose left-to-right or right-to-left. You have to check explain to see the order.
For joins there shoud be no difference in explain when you change the order (unless there are outer joins, but this might return different
result sets)
Dieter
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