--多表查詢 select employees.employee_id,employees.department_id,departments.department_name from departments,employees where employees.department_id=departments.department_id;

運行結(jié)果

--多表查詢 其他情況 select e.employee_id,e.department_id,d.department_name from departments d,employees e where e.department_id=d.department_id; --多表查詢 其他情況 select employee_id,e.department_id,department_name from departments d,employees e where e.department_id=d.department_id;

運行結(jié)果

--員工在什么城市工作 三個表連接 select employee_id,e.department_id,department_name，city from departments d,employees e,locations l where e.department_id=d.department_id and d.location_id=l.location_id

運行結(jié)果

--根據(jù)檔次轉(zhuǎn)換 非等式連接 select employee_id,last_name,salary,grade_level from employees e,job_grades j where e.salary between j.lowest_sal and j.highest_sal

運行結(jié)果

外連接

--多表查詢 外連接 select employee_id,e.department_id,department_name from departments d,employees e where e.department_id=d.department_id(+)

運行結(jié)果

--多表查詢 右外連接 select employee_id,e.department_id,department_name from departments d,employees e where e.department_id(+)=d.department_id

運行結(jié)果

--自然連接 select employee_id,department_id,department_name from employees join departments using(department_id)

運行結(jié)果

--自然連接 select employee_id,d.department_id,department_name from employees e join departments d on e.department_id=d.department_id

運行結(jié)果

--自然連接 三表連接 select employee_id,d.department_id,department_name from employees e join departments d on e.department_id=d.department_id join locations l on d.location_id=l.location_id

運行結(jié)果

--自然連接 左外 select employee_id,d.department_id,department_name from employees e left outer join departments d on e.department_id=d.department_id

運行結(jié)果

--自連接 --查詢公司中員工'chen'的manager信息 select emp.last_name,manager.last_name,manager.salary,manager.email from employees emp,employees manager where emp.manager_id=manager.employee_id and lower(emp.last_name)='chen'

運行結(jié)果

總結(jié)

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