Dropping and creating new columns

• Rootman

  SSCrazy

  Points: 2641

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  March 10, 2008 at 1:50 pm

  #120694

  Hello,

  I have inherited a script which creates new columns on a table, and then drops some other columns on the same table.

  My question is, would there be any performance improvement, if I were to drop the unwanted columns first, before adding the new columns?

  Thanks

• Johan Bijnens

  SSC Guru

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  March 10, 2008 at 2:06 pm

  #787587

  Maybe.

  If you add columns not null with an actual default value, rows will be rewritten, so in that case, yes , then the old columns will be gone.

  Otherwise no because the drop column is only a "logical" drop.

  Only at maintenance time (rebuild or maintenanceplan) rows will be

  rewritten according to the new columns.

  Johan
  
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