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'.
Video on the cost of concrete floors. Depending on the level of complexity, concrete floors can cost as little as $2 to $6 a square foot or be as expensive as $15 to $30 a square foot.s the chart below shows, the average per-square-foot costs of basic stained or polished concrete floors are competitive with what you would expect to pay to install linoleum, vinyl flooring, ceramic tile and high-quality carpeting.