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'.
The average cost of a concrete slab will be between $5 and $7 dollars per square foot or $135 and $189 per cubic yard.he average cost of a concrete slab will be between $5 and $7 dollars per square foot or $135 and $189 per cubic yard.