Joins, Joins, Joins

• SQLSACT

  SSC-Insane

  Points: 21838

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  January 16, 2013 at 7:17 am

  #287971

  Hi All

  I am trying to clear up my understanding about joins

  Consider the following query

  select Table1.Col1 from Table1

  inner join Table2

  on Table1.Col1 = Table2.Col1

  where Table1.Col1 < '3000'

  Is this the rough order of things:

  >> where predicate is applied to Table1.Col1

  >> where predicate is applied to Table2.Col1

  >> results of each is cross referenced, outputting matches

  I am almost certain that this is what's happening here, am I correct?

  Thanks

• PiMané

  SSChampion

  Points: 13965

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  January 16, 2013 at 7:36 am

  #1577820

  Take a look at the Execution Plan... That's what's happening..

  Pedro

  ---

  
  If you need to work better, try working less...

• SQLSACT

  SSC-Insane

  Points: 21838

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  January 16, 2013 at 7:38 am

  #1577822

  PiMané (1/16/2013)

  ---

  Take a look at the Execution Plan... That's what's happening..

  Pedro

  I have had a look at the execution plan and it seems that as I described is what is happening.

  Where I am a bit stuck is what happens when SQL decides to use a Nested Loop Join

• mister.magoo

  SSC-Forever

  Points: 47174

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  January 16, 2013 at 7:39 am

  #1577823

  PiMané (1/16/2013)

  ---

  Take a look at the Execution Plan... That's what's happening..

  Pedro

  like this one:

  

  But as Pedro intimated....it depends...look at the plan...

  MM
  

  ---

  
  select geometry::STGeomFromWKB(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