oracle学习笔记四

SELECT table1.column, table2.column
FROM table1
[CROSS JOIN table2] |
[NATURAL JOIN table2] |
[JOIN table2 USING (column_name)] |
[JOIN table2
ON(table1.column_name = table2.column_name)] |
[LEFT|RIGHT|FULL OUTER JOIN table2
ON (table1.column_name = table2.column_name)];




交叉连接 CROSS JOIN
oracle 8i中
select * from employees,departments;
oracle 9i中
select * from employees CROSS JOIN departments;


自然连接 NATURAL JOIN
oracle 8i
select * from emp e,dept d where e.deptno=d.deptno;
oracle 9i
select * from emp NATURAL JOIN dept;

select * from emp join dept using (deptno);
on子名
sql-1999
select * from emp;
select * from dept;
select e.ename,e.empno,d.dname,d.deptno
from emp e join dept d on(e.deptno=d.deptno);

三个表的内连接
select * from employees;
select * from location;
select * from departments;
oracle8i等值接连
select e.employee_id,e.first_name||e.last_name,d.department_id,d.department_name,l.loc,l.city
from employees e,departments d,location l where e.department_id=d.department_id and d.location_id=l.location_id;
sql-1999
select e.employee_id,e.first_name||e.last_name,d.department_id,d.department_name,l.loc,l.city
from employees e join departments d on(e.department_id=d.department_id) join location l on(d.location_id=l.location_id);



左外连接 LEFT OUTER JOIN 对连接条件中左边的表中的记录不加限制
oracle8i右外接连
select e.employee_id,e.first_name||e.last_name,d.department_id,d.department_name
from employees e, departments d where e.department_id=d.department_id(+);
sql-1999
select e.employee_id,e.first_name||e.last_name,d.department_id,d.department_name
from employees e left outer join departments d on(e.department_id=d.department_id);

右外连接 RIGHT OUTER JOIN 对连接条件中右边的表中的记录不加限制
oracle8i左外接连
select e.employee_id,e.first_name||e.last_name,d.department_id,d.department_name
from employees e, departments d where e.department_id(+)=d.department_id;
sql-1999
select e.employee_id,e.first_name||e.last_name,d.department_id,d.department_name
from employees e right outer join departments d on(e.department_id=d.department_id);

全外连接 Full outer Join 全外连接是对两个表中的记录都不加限制。
select e.employee_id,e.first_name||e.last_name,d.department_id,d.department_name
from employees e full outer join departments d on(e.department_id=d.department_id);