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 cost of concrete floors is very low about $ 2 to $ 6 per square foot to polish a plain gray slab giving it a lustrous sheen the concrete s tonal differences subtle cracks and aggregates take on a stonelike natural feel