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'.
Concrete Costs & Prices We have collected data nationwide to help calculate the average cost of concrete in the US. The following are average costs and prices reported back to us: $6.40 per square foot (4 inch reinforced slab on grade) (Range: $6.02 - $6.77) $8.21 per square foot (6 inch reinforced slab on grade) (Range: $6.75 - $9.67)