query to find keys in a table

hi

i have this query which tells what are the primary keys in a table

SELECT cols.table_name, cols.column_name, cols.position, cons.status, cons.owner
FROM all_constraints cons, all_cons_columns cols
WHERE cols.table_name = 'PERSON_DATA'
AND cons.constraint_type = 'P'
AND cons.constraint_name = cols.constraint_name
AND cons.owner = cols.owner
ORDER BY cols.table_name, cols.position;

Any one care to explain what are the tables : all_constraints and all_cons_columns
and what is cons.constraint_type = 'P'

Thanks
royjaydAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

slightwv (䄆 Netminder) Commented:
>>all_constraints
>>all_cons_columns
>>cons.constraint_type = 'P'

All of this is in the docs:
http://docs.oracle.com/cd/E11882_01/server.112/e25513/statviews_1046.htm

http://docs.oracle.com/cd/E11882_01/server.112/e25513/statviews_1044.htm
0
royjaydAuthor Commented:
slightwv

A simple one or two liners with a layman explanation would have helped :-)
0
slightwv (䄆 Netminder) Commented:
I'm not sure I could have explained it better than the docs do.
0
awking00Information Technology SpecialistCommented:
all_constraints and all_cons_columns are system dictionay views containing metadata of the database. The all_ prefix allows you to get information on objects that you own or have access to (the dba_ prefix is for all objects and the user_prefix is only for objects you own).
The constraint_type values available are:
C - Check constraint on a table
P - Primary key
U - Unique key
R - Referential integrity
V - With check option, on a view
O - With read only, on a view
H - Hash expression
F - Constraint that involves a REF column
S - Supplemental logging

Some additional links -
http://psoug.org/reference/constraints.html
http://docs.oracle.com/cd/B28359_01/server.111/b28320/statviews_1042.htm
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
royjaydAuthor Commented:
thanks.
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Oracle Database

From novice to tech pro — start learning today.