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'.
Basic, construction-grade concrete costs about $5 to $10 per square foot, including installation. Opting for fancier, decorative versions such as stamped or colored concrete will add several dollars per square foot to the price. Very high-end concrete could cost as much as $15 per square foot.