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GeneralRequesting for a link for web services basics... Pin
Sushil D Jadhav14-Sep-07 0:26
Sushil D Jadhav14-Sep-07 0:26 
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QuestionADO.NET free E-books Pin
Vimalsoft(Pty) Ltd14-Sep-07 0:04
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QuestionJoin and Nested Query Pin
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Colin Angus Mackay14-Sep-07 0:10
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DLM@TD14-Sep-07 11:01
DLM@TD14-Sep-07 11:01 
Hi,

it is very hard to find a general answer on your question and it really depends on the situation and database schema behind (indexes at most). If you are trying to join two tables with, let's say more than 30 millions of records it will take forever, but if you have a good filtering on the second one and than using that in subquery it will fly. On other way, in a lot of situations, for example, SQL Server will treat your subquery as separate one and perform a separate optimization plan which costs time. There are two different types of subqueries, self-contained (run independently of the outer query) and correlated ones (have references to outer query columns) and they also behave differently. The same is for joins. SQL Server now has a couple of join algorithms used by query optimizer (loop join, merge join and hash join) in different situation.
To get a real answer in a particular situation, is possible by just examine execution plan for both queries and than decide which one to use.
In addition to this, I would always consider using CTE (Common table Expressions) (at least on SQL Server 2005) as one of the most effective ways of subquerying.
Hope this helps a little bit.
Best regards,
DLM@bypsoft.com

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Questionarray in a asp Pin
nicetohaveyou13-Sep-07 21:07
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QuestionSql Reporting Services viewer refresh problem Pin
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QuestionConnection Error [modified] Pin
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QuestionStored Procedures - Validating Variables Pin
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