The view constraint_table_usage identifies all tables in the current database that are used by some constraint and are owned by a currently enabled role. (This is different from the view table_constraints, which identifies all table constraints along with the table they are defined on.) For a foreign key constraint, this view identifies the table that the foreign key references. For a unique or primary key constraint, this view simply identifies the table the constraint belongs to. Check constraints and not-null constraints are not included in this view.
Table 34-16. constraint_table_usage Columns
|table_catalog||sql_identifier||Name of the database that contains the table that is used by some constraint (always the current database)|
|table_schema||sql_identifier||Name of the schema that contains the table that is used by some constraint|
|table_name||sql_identifier||Name of the table that is used by some constraint|
|constraint_catalog||sql_identifier||Name of the database that contains the constraint (always the current database)|
|constraint_schema||sql_identifier||Name of the schema that contains the constraint|
|constraint_name||sql_identifier||Name of the constraint|