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'.
A 230 square foot concrete slab costs between 1,200 dollars and  1,500 dollars. The variance depends on labor and materials in your  area. 230 square foot concrete slab costs between 1,200 dollars and  1,500 dollars. The variance depends on labor and materials in your  area.