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I have 2 sql's (each sql is about 10 lines joining about 5 tables). These 2 sqls returns same column. I want to execute sql2 only if sql1 returns no result.

How to do this in one sql?

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  • Please post up the SQL statements. Commented Sep 7, 2011 at 8:54

1 Answer 1

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query1
UNION ALL
( query2
   WHERE NOT EXIST (query1)
)

In Oracle you can also factor:

WITH conditional_query AS (query1)
SELECT * FROM conditional_query
UNION ALL
( query2 WHERE NOT EXIST (SELECT NULL FROM conditional_query) )
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1 Comment

well, I end up using coalesce. Thanks for your idea

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