HIVE的基础知识内部表与外部表

HIVE:将结构化的数据文件映射为数据库表
查询语句简便话，类SQL语言；
表在hdfs中表现为文件夹

准备工作(要先启动hadoop和zookeeper)

[root@hadoop151 hive]# jps
15105 Jps
7715 NodeManager
2855 QuorumPeerMain
7303 DataNode
7179 NameNode
7455 SecondaryNameNode
7599 ResourceManager

启动之后应该要有的程序

启动HIVE

[root@hadoop151 hive]# nohup hive --service hiveserver2 &


[root@hadoop151 hive]# hive                  //hive命令行
[root@hadoop151 hive]# beeline -u "jdbc:hive2://localhost:10000"                //Beeline

上面两种启动的方式选其一即可，beeline里面显示表格有框

HIVE表里的基本数据类型

int 
double
decimal
boolean
string             //字符串
date            
timestamp           //时间戳

数据表

内部表

hdfs中为所属数据库目录下的子文件夹
删除表会删除数据
示例：

hive>create database myhive;
hive> use myhive;
hive> create table if not exists user(id int,name string);
hive> insert into user values(1,"yang");

这是插入成功的状态，数据存放在表的目录下

hive> drop table user;

删除表之后，发现数据也被删除

外部表

数据保存在指定位置的hdfs路径中
删除表不会删除数据

实例：

现有如下数据

2020-7-716:11:47|12345|{enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:11:53|12345|{enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:12:0|12345|{enventName:click_img_cat,pageName:http://localhost:8080/index.html}

把它放到.log文件中

!hdfs dfs -mkdir /customers
!hdfs dfs -put action.log /customers
!hdfs dfs -chmod 777 /customers

hive> create external table if not exists usernew(
    > date string,
    > id string,
    > msg string
    > )
    > row format delimited fields terminated by "|"
    > location "/customers";
OK
Time taken: 0.115 seconds
hive> select * from usernew;
OK
2020-7-716:11:47        12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:11:53        12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:12:0 12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:12:1 12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:12:3 12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:12:5 12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:12:10        12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:20:59        12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:21:0 12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:21:3 12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:21:4 12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:21:24        12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
2020-7-716:21:25        12345   {enventName:click_img_cat,pageName:http://localhost:8080/index.html}
Time taken: 0.106 seconds, Fetched: 13 row(s)

hive> drop table usernew;

删除之后文件还在

退出

！q
quit;    //都可以