User Constraint Table

User Constraint Table:- A table can be created with multiple constraints attached to its columns. If the user wishes to see the table structure, oracle provides the describe command. But this command displays only the columns names data type size and the not null constraint.
            The information about the other constraints that may be attached to the table columns such as primary key,foreign key ,etc..Oracle stores such information in a structure called USER_CONSTRAINTS.
The structure of the user_constraints table:-
            Owner
            Constraint_name
            Constraint_type
            Table_name
            Search_condition
            R_Owner
            R_constraint_name
Syn:-    select * from user_constraints where table_name=’user tablename’;

Ex:-1)  select owner,table_name,constraint_type,constraint_name from
user_constraints;
2) select owner,table_name,constraint_type,constraint_name from
user_constraints where table_name=’EMP’;

Constraint_type:-
            P          à Primary key
            R         à Foreign key
            U         à Unique Key
            C         à Check

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