question about histograms for CBO

Is it possible to create a histogram that will take into account the distribution of data across multiple columns or just a single column at a time?

I'm specifically trying to understand the following statement:

analyze table test estimate statistics for columns col_1,col_2,col3 size 10;

This statement is syntactically correct and it works, but I really don't know what it did.

Is it the same as running individual histograms on the columns:

analyze table test estimate statistics for columns col_1 size 10;
analyze table test estimate statistics for columns col_2 size 10;
analyze table test estimate statistics for columns col_3 size 10;

Or by placing all columns in one statement, am I getting a different histogram that is somehow analyzing and bucketizing all three columns together?

A good example would probably be a demographic table with last_name, age and gender.

Thanks for any help,
Gavin

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Before you buy. Received on Fri Sep 15 2000 - 15:30:31 CDT