Xref: alice comp.databases.oracle.server:19236 Path: alice!news-feed.fnsi.net!newsfeed.wli.net!su-news-hub1.bbnplanet.com!atl-news-feed1.bbnplanet.com!news.bbnplanet.com!news.ipass.net!not-for-mail From: "David Sisk" Newsgroups: comp.databases.oracle.server References: <35376D45.16ED@w-4.de> Subject: Re: SQL-statment tuning Lines: 30 X-Newsreader: Microsoft Outlook Express 4.71.1712.3 X-MimeOLE: Produced By Microsoft MimeOLE V4.71.1712.3 Message-ID: Date: Fri, 17 Apr 1998 21:02:28 GMT NNTP-Posting-Date: Fri, 17 Apr 1998 17:02:28 EDT "SELECT * FROM table WHERE tab_column = 1" would use a B-tree index if the selectivity of tab_column is reasonably high OR a bitmap index if the selectivity of tab_column is very low (<1%). "SELECT * FROM table WHERE tab_column IS NULL" cannot possibly use an index. If tab_column of row x is null, then the rowid of row x is not contained in the index, so there's nothing in the index to read. Try rewriting the statement without using the IS NULL. Good luck, Dave Jürgen Kling wrote in message <35376D45.16ED@w-4.de>... >Who can help me to optimize the following SQL statment: > >select * from TABLE >where TAB_COLUMN = 1 > or TAB_COLUMN is null > > >the Column TAB_COLUMN havein an index, but Oracle can't use it. >Thus Oracle do an Full Table scan. > >Do somebody now how to change this statement > > >jkling@w-4.de