All purchases made by the city for materials, supplies, services, repairs, construction, or ocher items shall be made in accordance with a procurement code, which shall be adopted by ordinance by the board of mayor and aldermen. The procurement code shall promote fair and equitable treatment to all suppliers or prospective suppliers of goods or services, promote effective competition among prospective suppliers of goods and services, make as uniform as possible the procedures among various departments and agencies of the city, and promote the economical, effective, and efficient use of the city's total resources.