What is the diff. between NUM_ROWS in DBA_INDEXES and DBA_TABLES
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Thread: What is the diff. between NUM_ROWS in DBA_INDEXES and DBA_TABLES

  1. #1
    Join Date
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    Unhappy

    Hi guys,

    What is the diff. between NUM_ROWS in DBA_INDEXES and DBA_TABLES.

    Also, does any one have sizing formula for B*tree indexes?

    Thanks in Adv.





    Sam
    ------------------------
    To handle yourself, use your head. To handle others, use your heart

  2. #2
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    dba_tables tells you number of rows you have in the table
    dba_indexes tells you how many rows is stored in index

    because index do not store nulls you see different results

  3. #3
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    Originally posted by samdba
    What is the diff. between NUM_ROWS in DBA_INDEXES and DBA_TABLES.
    NUM_ROWS in DBA_TABLES shows the count of all rows in the table. The same column in DBA_INDEXES on the other hand shows the number or rows in the table that have an entry in that index. As you know, B*Tree index does not store index entries for rows taht have NULLs in all columns that comprise the index, so the number in DBA_INDEXES could be smaller than the one in DBA_TABLES if indexed collumns contain NULLs.
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

  4. #4
    Join Date
    Jan 2002
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    DBA_INDEXES:
    NUM_ROWS NUMBER Number of rows in the index

    DBA_TABLES:
    NUM_ROWS NUMBER Number of rows in the table


    The concepts guide talks about how the B*tree indexes are
    stored and under what conditions key compression can
    be used to reduce storage requirements.

    --
    Paul

  5. #5
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    Thanks to all of you,

    Does any one have sizing formula for B*tree indexes?

    Thanks.

    Sam
    ------------------------
    To handle yourself, use your head. To handle others, use your heart

  6. #6
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    I dont because I dont size segments anymore with LMT....

  7. #7
    Join Date
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    3,131

    Question

    Should someone mention that in both cases NUM_ROWS is only as accurate as you last analyze?

    MH
    I remember when this place was cool.

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