bitmap index
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  1. #1
    Join Date
    Feb 2001
    Posts
    103
    Hi,
    Can anyone tell me what is bitmap index. I will appreciate if an example is provided with the reply.

    thankx in advance.
    When the going gets tough, the tough gets going

  2. #2
    Join Date
    Mar 2001
    Posts
    5

    Post bitmap

    The advantage of bitmap index are greatest for low cardinality columns i.e, if the values in a column are repated more than a hundred times, the column is a candidate for a bitmap index

    syntax:
    CREATE BITMAP INDEX ON ();

    EXAML\PLE:

    CREATE BITMAP INDEX V1_INDX ON ORDERS(ORDERNO);

  3. #3
    Join Date
    May 2000
    Location
    Delhi
    Posts
    108
    hi akhil

    The principle of a bitmap index is the use of a matrix, which has columns corresponding to all data values in the column. Thus, if the column contains only three distinct values, the bitmap index can be visualized as containing a column for the ROWID and three columns, one for each distinct value. Figure 4-3 displays a pictorial representation of a bitmap index containing three distinct values. The physical representation of the bitmap index is not far from the picture. Since each distinct value adds to the size of the index, bitmap indexes work best when there are few distinct values allowed for a column. Thus, the bitmap index improves performance in situations where B-tree indexes are not useful, and vice-versa.

    Bit set in this column indicates row has this value set for the column

    regards
    Amit

  4. #4
    Join Date
    Jul 2013
    Posts
    1
    Akhil, there's also a good description here as well:

    http://www.programmerinterview.com/i...-bitmap-index/

  5. #5
    Join Date
    Nov 2000
    Location
    Pittsburgh, PA
    Posts
    4,001
    If you have an OLTP database. you may also want to look at the performance implications of bitmap indexes in OLTP databases.
    this space intentionally left blank

  6. #6
    Join Date
    Jul 2002
    Location
    Lake Worth, FL
    Posts
    1,477

    Thumbs down

    Wow a post from 03-29-2001 ( The Phoenix ) has been resurrected.
    "The person who says it cannot be done should not interrupt the person doing it." --Chinese Proverb

  7. #7
    Join Date
    Nov 2000
    Location
    Pittsburgh, PA
    Posts
    4,001
    Quote Originally Posted by LKBrwn_DBA View Post
    Wow a post from 03-29-2001 ( The Phoenix ) has been resurrected.
    I usually catch on to the old post. I guess I picked a bad week to stop sniffing glue...
    this space intentionally left blank

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