/*+XXXXX*/的具體含義？

流云飛渡

9I中新增的這個/*+XXXXX*/的具體含義是什么？
例：SQL>;select /*+CACHE*/ename from scott.emp;

tinywind

這是hint,提供了執(zhí)行sql時更細微的控制,這個語句是讓結果保留在cache中

hint不是9i中加入，很早就有，現(xiàn)在oracle已經(jīng)不推薦使用hint了

流云飛渡

能給個鏈接或更詳細的解釋嗎？

tinywind

去查oracle的文檔，我以前在8的文檔中看到過

流云飛渡

查過了，沒查到，所以才發(fā)的帖子

mydeer

為什么不推薦hint？？

sshd

In general oracle optimizer will control how to execute a sql. Sometimes a user may choose to bypass that and tell oracle to execute the sql in the way he suggested. Thus he can use hint /*+ ... */ to achive that.
Note if any thing is wrong in the hint oracle just ingore it and you will not get any error.