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 concrete slab cost. I'll base my price on what my actual estimate would be to install a 6 thick concrete slab for one of my customers. Base cost for a 6 thick concrete slab -- $4.00 dollars per square foot --. Take the length of the concrete slab x the width of the slab to get the. total square footage. Multiply the total square footage by 4 (dollars) to get the total price.