刚开始进去后,我是懵逼的状态,不知道要干嘛,之前常用的是MSSQL,感觉两者还是有区别的: oracle中:1.查询数据库名:select name,dbid from v$database;或者show parameter db_name;2.查询实例名:select instance_name from v$instance;或者show parameter instance_name;3.查询数据库域名:select value from v$parameter where name='d…
一.Hadoop Shell命令 既然有官方文档,那当然先找到官方文档的参考:http://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/FileSystemShell.html 对于3种命令的区别: 以下内容参考自stackoverflow Following are the three commands which appears same but have minute differences hadoop…
一.子查询 1.子查询语法 SELECT select_list FROM table WHERE expr operator (SELECT select_list FROM table) 示例: SELECT LAST_NAME FROM employees WHERE salary > (SELECT salary FROM employees WHERE LAST_NAME = 'Abel') 2.子查询示例 使用组函数:查询最低工资的员工信息 SELECT LAST_NAME,sala…
一.概述 根据之前的凡技术必登其官网的原则,我们当然先得找到它的官网:http://hadoop.apache.org/ 1.什么是hadoop 先看官网介绍: The Apache™ Hadoop® project develops open-source software for reliable, scalable, distributed computing. The Apache Hadoop software library is a framework that allows fo…
之前安装好数据库后,会有下面这个弹窗,然后根据Database Control URL地址进入瞧一瞧,看一看! 根据地址进入以后,是一个登录界面,用system账户登录,密码就是安装Oracle的时候设置的密码 进去以后就是一个总的预览界面,以前一直是用PLSQL软件连接或者直接cmd命令,原来有这个可视化操作页面!…