The key fields are underlined, and the domain of each field is listed after the field name. Thus, SID is the key for SUPPLIERS, PID is the key for PARTS, and SID and PID together form the key for CATALOG. The CATALOG relation lists the prices charged for parts by suppliers. CATALOG. SID is a foreign key referring to SUPPLIERS. SID and CATALOG. PID is a foreign key referring to PARTS. PID. Write the following queries in SQL.