31. The primary keys within a database are used to define the relationships among the tables. 32. Therefore, most physical implementations have a unique primary key ( PK ) for each table. 33. Primary keys were added to the SQL standard mainly as a convenience to the application programmer.34. The primary key in the first may be associated with multiple primary keys in the second. 35. The primary key in the first may be associated with multiple primary keys in the second. 36. Consider a database where each operation begins with a lookup of a record s primary key . 37. Other types of constraints ( unique, primary key , and foreign key constraints ) are not inherited. 38. The primary key to success in a kiosk or RMU is low SKUs and higher transaction totals. 39. In a row-oriented indexed system, the primary key is the rowid that is mapped to indexed data. 40. Secondary indexes have primary keys at their leaves to logically link to the record in the primary index.
