在Oracle中强制索引 [英] Forcing an index in oracle

问题描述

我有一个查询，其中包含许多字段.出于某种奇怪的原因，一个表的索引根本没有使用(我清楚地使用了索引键)，而是进行了全表扫描.我想强制索引.我们曾经在sybase中做优化器提示. oracle中有类似的提示吗? 例如，在sybase中加入表a，b，c并在表a中使用myindex，我会这样做:

I have a query joining lots of fields. For some strange reason the index for one table is not being used at all( I use the index key clearly), instead it is doing a FULL table scan. I would like to force the index. We used to do optimizer hints in sybase. Is there a similar hint available in oracle? For example, in sybase to join tables a, b, c and use myindex in table a, I would do :

SELECT a.*
FROM     a(INDEX myindex),
         b,
         c
WHERE    a.field1 = b.field1
AND      b.field1 = c.field1

问题是我该如何在oracle中执行此操作. 谢谢 萨罗

Question is how do I do this in oracle. Thanks Saro

推荐答案

是的，Oracle中有类似的提示.看起来像这样:

Yes, there is a hint like that in Oracle. It looks something like this:

select /*+ index(a my_index) */ from a

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