A primary key is a candidate key that is most appropriate to be the main reference key for the table. As its name suggests, it is the primary key of reference for the table and is used throughout the database to help establish relationships with other tables.
1 A concrete driveway with several decorative elements can cost $12 -$18 a square foot, or $3,600 -$5,400 for 12'x25' or $11,500 -$17,500 for 24'x40'.
1 On average, getting concrete floors can cost anywhere from as little as $2 to as much as $17 per square foot. 2  An economical option, which can just change the tone of the concrete floor, will typically cost less than $6.