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'.
Those opting for hand coloring, unique angles or a special design will see the price rise to more than $15 per square foot. The average price that homeowners pay for a concrete patio is around $2,800 to just over $4,000, but some homeowners report spending as little as $1,000 or as much as $6,500.A custom design typically costs more because those projects involve more work.asic concrete patio costs: $6 to $10 per square foot. Custom concrete patio costs: $10 to $15 per square foot. Advanced or complex designs: $15 or more per square foot. Average patio costs: $2,800 to $4,000.