Histograms: They're automatically generated for all columns on

Listers,

Here's an interesting fact about histograms that I was unaware of (and I bet most
of you are unaware of too).

When a table is just plain analyzed, histograms are automatically created with a bucket size of 1 for each column in each table. You can see these buckets/histograms by querying the dba_tab_columns table and the dba_tab_histograms(Oracle 8+) or the dba_histograms (pre-Oracle8) table .

Apparently a single-bucket histogram is the same as having no histogram. There is basically no effect on the explain plan when you have a single-bucket histogram because all of the possible values for the histogram are in the same bucket.

I discovered this from an obscure newsgroup post while searching Metalink. Received on Wed Aug 16 2000 - 08:28:25 CDT