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  • (三)Oracle学习笔记—— sql语句

    0. scott 用户默认表介绍

    scott用户Tables目录下包含四张表

    1. insert(插入)语句

    给指定列插入数据:

    insert into dept(deptno,dname) values(50,'xx');

    插入全部列数据:

    insert into dept(deptno,dname,loc) values(60,'xx','lll');

    2. update(更新)语句

    update dept set dname='司法部' where deptno=50;
    update dept set dname='司法部' ,loc='china' where deptno=50;

    3. delete(删除)语句

    删除指定数据:

    delete from dept where deptno=70;

    删除指定条件的数据:

    delete from dept where deptno>40;

    4. select(查询)语句

    查询所有:

    select * from emp;

    指定字段查询:

    select ename,sal from emp;

    简写 

    insert into dept values(70,'xxx','llll');

    加 where 条件:

    select * from emp where sal>=800;
    select * from emp where sal>=1500 and job='SALESMAN';

    Distinct 去重复记录;

    Group by 分组查询:select job,count(ename) as num from EMP t group by job;

    Having 过滤分组:select job,count(ename) as num from EMP t group by job having count(ename)>=2;

    Order by 排序:select * from emp order by sal desc;

    子查询:查询出基本工资大于平均工资的员工:select * from emp where sal>(select avg(sal) from emp)

    联合查询:

    并集(去重复):

    select * from t_user1
    union
    select * from t_user2;

    并集:

    select * from t_user1
    union all
    select * from t_user2;

    交集:

    select * from t_user1
    intersect
    select * from t_user2;

    差集:

    select * from t_user1
    minus
    select * from t_user2;

    内连接:

    select * from emp t,dept d where t.deptno=d.deptno;

    类似:select * from emp e inner join dept d on e.deptno=d.deptno; inner 可以省略;

    外连接:

    左外连接:select * from emp e left join dept d on e.deptno=d.deptno;

    右外连接:select * from emp e right join dept d on e.deptno=d.deptno;

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  • 原文地址:https://www.cnblogs.com/zjfjava/p/7169334.html
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