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Spotlight on Oracle 10.10 - Release Notes

Set Operations

The following table shows some of the common set operations you may encounter while using the Explain SQL window.

Operation Description

CONCATENATION

Multiple result sets are merged in the same way as in an explicit UNION statement. This typically occurs when an OR statement is used with indexed columns.

INTERSECTION

Two result sets are compared, and only rows common to both are returned. This operation usually only takes place as a result of an explicit use of the INTERSECTION clause.

MINUS

All result sets in the first result set are returned, except those appearing in the second result set. This occurs as a result of the MINUS set operator.

UNION-ALL

Two result sets are combined and rows from both returned.

UNION

Two result sets are combined and rows from both are returned. Duplicate rows are not returned.

VIEW

Either a view definition has accessed, or a temporary table has been created to store a result set.

 

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