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AI Feature GuideAI4DB: Autonomous Database O&MABO OptimizerIntelligent Cardinality EstimationOverview
Overview
SQL Rewriter is an SQL rewriting tool. It converts query statements into more efficient or standard forms based on preset rules to improve query efficiency.
NOTE:
- This function does not apply to statements that contain subqueries.
- This function supports only the SELECT and DELETE statements for deleting the entire table.
- This function contains 11 rewriting rules. Statements that do not comply with the rewriting rules are not processed.
- This function displays original query statements and rewritten statements on the screen. You are not advised to rewrite SQL statements that contain sensitive information.
- The rule for converting UNION to UNION ALL avoids deduplication and improves the query performance. The obtained result may be redundant.
- If a statement contains ORDER BY + specified column name or GROUP BY + specified column name, the SelfJoin rule is not applicable.
- The tool does not ensure equivalent conversion of query statements. The purpose is to improve the efficiency of query statements.
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