https://www.xifenfei.com/2012/04/hint%e6%8c%87%e5%ae%9aindex%e7%9a%84%e6%b7%b1%e5%85%a5%e7%90%86%e8%a7%a3.html 提供7*24专业数据库(Oracle,SQL Server,MySQL,PostgreSQL等)恢复和技术支持@Tel:17813235971 Thu, 11 Dec 2025 02:46:14 +0000 hourly 1 https://www.xifenfei.com/2012/04/hint%e6%8c%87%e5%ae%9aindex%e7%9a%84%e6%b7%b1%e5%85%a5%e7%90%86%e8%a7%a3.html/comment-page-1#comment-771 Mon, 09 Apr 2012 02:46:52 +0000 https://www.xifenfei.com/?p=2865#comment-771 If the INDEX hint specifies a single available index, then the database performs a scan on this index. The optimizer does not consider a full table scan or a scan of another index on the table.

For a hint on a combination of multiple indexes, Oracle recommends using INDEX_COMBINE rather than INDEX, because it is a more versatile hint. If the INDEX hint specifies a list of available indexes, then the optimizer considers the cost of a scan on each index in the list and then performs the index scan with the lowest cost. The database can also choose to scan multiple indexes from this list and merge the results, if such an access path has the lowest cost. The database does not consider a full table scan or a scan on an index not listed in the hint.

If the INDEX hint specifies no indexes, then the optimizer considers the cost of a scan on each available index on the table and then performs the index scan with the lowest cost. The database can also choose to scan multiple indexes and merge the results, if such an access path has the lowest cost. The optimizer does not consider a full table scan.

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