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Article:
  Introducing SQL Sets
Subject:   Doubt in union operator
Date:   2001-10-09 20:23:15
From:   suresh175
We are using UNION operator for getting the result from 2 sql statements. If one of the sql statements returns zero rows, then whole sql statement almost hangs, i.e. it takes more than 2hrs. If both the sql statement returns value it takes less that an minute. Could you please provide as the reason why it is so ?