Basic Query Structure A typical SQL query has the form: select A,A2,...,An from r,r2,...rm where P A,represents an attribute R,represents a relation 。P is a predicate. The result of an SQL query is a relation. Database System Concepts-7th Edition 3.12 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 3.12 ©Silberschatz, Korth and Sudarshan th Edition Basic Query Structure ▪ A typical SQL query has the form: select A1 , A2 , ..., An from r1 , r2 , ..., rm where P • Ai represents an attribute • Ri represents a relation • P is a predicate. ▪ The result of an SQL query is a relation