一些习题,有助于加深SQL查询。 Relational algebra and SQL Query Consider the following schema of a company database: Employees(eid, ename, address, supereid) Departments(did, dname) Projects(pid, pname, did) Works_on(eid, pid, hours) (1)For each employee, find hi
第一章:写简单的sql语句 SQL> alter user scott account unlock; SQL> alter user scott identified by tiger; SQL> conn scott tiger 1 使用算术操作符 SELECT last name salary salary + 300 FROM employees; 7 使用interval CREATE TABLE warranty prod id number warranty t
例如:按照 department id 查询 employees 员工表 和 departments 部门表 的信息 方式一 通用型 :SELECT FROM WHERE SELECT e last name e department id d department name FROM employees e departments d where e department id d department id 方式二:SELECT FROM NATURAL JOIN 有局限性:会自动连接两个