Avoid multiple scan of the same table

Giganews Newsgroups
Subject: Avoid multiple scan of the same table
Posted by:  maks…@gmail.com
Date: Thu, 21 Aug 2008

Is there way to avoid multiple scan of the same table in following?

Select c1 as v1, c2 as v2, c3 as v3
From t1
Union
Select c1 as v1, c2 as v2, c4 as v3
From t1
Where  c5 < 5000

The output should look like..

v1, v2, v3
v11, v21, v31
v12, v22, v32
and so on.

Rows from the both queries can be same so UNION is required to avoid
duplicates in current construct.

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