Try the SQL command below:

SELECT COL.CONSTRAINT_NAME,COL.COLUMN_NAME,CON.CONSTRAINT_TYPE
FROM USER_CONS_COLUMNS COL, USER_CONSTRAINTS CON
WHERE COL.TABLE_NAME = upper('TABLE_NAME')
AND COL.TABLE_NAME = CON.TABLE_NAME
AND COL.CONSTRAINT_NAME = CON.CONSTRAINT_NAME
AND CON.CONSTRAINT_TYPE='P';

It will be shown the primary key of a table.

TheStone.

B.