orale培训教材包括了所有的sql说明和实例

				-- NOT NULL CONSTRAINT
				ALTER TABLE plsql101_person MODIFY (first_name NOT NULL);
				ALTER TABLE plsql101_person MODIFY (last_name NOT NULL);
				
				INSERT INTO plsql101_person VALUES (
				     'XL', 'Xaviera', NULL, '15-10月-03'
				     )
				;