5.11.1 Equivalent exchange for a comparison predicate with row value constructors (conversion to a condition without row value constructors)
If a comparison predicate with row value constructors is specified in the search condition, the search condition undergoes equivalent exchange to become a condition without row value constructors. When a search condition undergoes equivalent exchange, the search condition sometimes becomes more effective in narrowing down the retrieval range.
The following shows examples of equivalent exchange. In the examples, C1 and C2 are column names.
- Organization of this subsection
(1) Example 1
![[Figure]](GRAPHICS/F0000050.GIF)
- Explanation:
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A condition with row value constructors undergoes equivalent exchange to become a condition without row value constructors.
(2) Example 2
![[Figure]](GRAPHICS/F0000051.GIF)
- Explanation:
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A != condition undergoes equivalent exchange to become a NOT condition.
(3) Format of conditions subject to equivalent exchange
The following shows the format of conditions that are subject to equivalent exchange:
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Comparison predicate
row-value-constructor comparison-operator row-value-constructor
If !=, ^=, or <> is specified as the comparison operator, equivalent exchange is performed using the logical operator NOT.