How To Determine Data Size Of A Table

Hi all I need a refresher, how do you determine the size of the data in the table?

Thanks

average row length and number of rows from user_tables, as long as you've recently analyzed.

thanks so much:)

or look at user_segments, will always be up to date

is that row num + average number of rows?

no, * not +

thanks! :)

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Originally Posted by davey23uk

or look at user_segments, will always be up to date

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... but possibly misleading, if you want the amount of data contained in the segment.

well a table is a segment no?

Yes, but it could be empty of data.

to find actual size of a table:
select count (distinct substr(rowid,1,15)) from schema.table_name

explanation:
each rowid references a block. Sum of all the distinct blocks give you the actual table size.

HTH

so hows is a COUNT = to a SUM

you query wil return the number of rows

Quote:

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Originally Posted by newbie

to find actual size of a table:
select count (distinct substr(rowid,1,15)) from schema.table_name

explanation:
each rowid references a block. Sum of all the distinct blocks give you the actual table size.

HTH

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Migrated and chained rows?

Quote:

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Originally Posted by slimdave

Migrated and chained rows?

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The method I presented is the table size in Oracle blocks -- that would exclude all empty blocks below the HWM. IMHO, I would consider any block that contains the pointer or the actual migrated/chained rows as non-empty data blocks.

Quote:

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Originally Posted by davey23uk

so hows is a COUNT = to a SUM

you query wil return the number of rows?

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Sorry for my poor usage. SUM in this context is the result of the query presented not the function SUM in oracle.