The Master Key
It turns out that Oracle's data dictionary is self-documenting.
When working with a properly created Oracle database, you can query the
dictionary
and dict_columns
views for descriptions of the
data dictionary views and their columns, a sort of meta-metadata. I
refer to these two views as the master key to
Oracle's data dictionary. To find the views giving information about a
particular class of database object, I find it helpful to perform a
wild-card search on the dictionary view's table_name
column. Example 10-16 shows this
approach being used to list views having to do with stored sequence
generators.
Example 10-16. Looking for data dictionary views describing sequences
COLUMN table_name FORMAT A20 COLUMN comments FORMAT A50 WORD_WRAPPED SELECT table_name, comments FROM dictionary WHERE table_name LIKE '%SEQUENCE%'; TABLE_NAME COMMENTS -------------------- -------------------------------------------------- USER_SEQUENCES Description of the user's own SEQUENCEs ALL_SEQUENCES Description of SEQUENCEs accessible to the user DBA_SEQUENCES Description of all SEQUENCEs in the database
The technique used in Example 10-16 is to search for view names containing the word "SEQUENCE".
Warning
Views aren't always named the way you think. The view describing a table's columns
is dba_tab_columns
; the word
table
has been abbreviated to
tab
. If you're interested in
information on Oracle object types, you'll find that many views with
names containing the word object
have nothing whatsoever ...
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