How can you determine the primary key using SQL?

If you have access to the SQL code which created the table the primary key can be seen easily. The primary key may be specified in one of two ways:

CREATE TABLE cia (name VARCHAR(10) PRIMARY KEY,
                 population INTEGER)

or, where the primary key is composite:

CREATE TABLE casting(movieid INTEGER,
                    actorid INTEGER,
                    PRIMARY KEY (movieid, actorid)
                    )

If this is not possible then implementation specific commands may work.

SELECT conkey
 FROM pg_constraint JOIN pg_class
  ON pg_class.oid=conrelid 
WHERE contype='p'
AND relname = 'casting'

SELECT a.owner, a.TABLE_NAME, b.column_name
  FROM all_constraints a, all_cons_columns b
 WHERE a.constraint_type='P'
   AND a.constraint_name=b.constraint_name
   AND a.TABLE_NAME = 'CASTING'

sp_pkeys @TABLE_NAME=casting

DESCRIBE casting

Meta Data

What are my tables?

What are the columns of the BBC table?