Big Data:
2022找工作是学历、能力和运气的超强结合体，遇到寒冬，大厂不招人，可能很多算法学生都得去找开发，测开
测开的话，你就得学数据库，sql，oracle，尤其sql要学，当然，像很多金融企业、安全机构啥的，他们必须要用oracle数据库
这oracle比sql安全，强大多了，所以你需要学习，最重要的，你要是考网络警察公务员，这玩意你不会就别去报名了，耽误时间！
与此同时，既然要考网警之数据分析应用岗，那必然要考数据挖掘基础知识，今天开始咱们就对数据挖掘方面的东西好生讲讲 最最最重要的就是大数据，什么行测和面试都是小问题，最难最最重要的就是大数据技术相关的知识笔试
Big data: hive data operation
create database if not exists myhive;
use myhive;
和sql类似的
show database;
desc database myhive;
create database myhive2 location '/myhive2';
自定义文件夹，放自己的地方
Delete is also drop
drop database myhive;
cascade;强制删除相关的表
create table test(id int);
建表之后就不能随便删除了
Hive data table operation
Similar to sql
create table test(id int, name string, gender string);
跟sql一样
drop table 表名；
easy
internal table operations
Metadata and its own data, the internal table, directly kill
the external table value to delete the metadata, and delete the data itself before sending
If there is no external, it is an internal table, and
the keyword modification is external
terminated by,,, split
delimited fields delimited column fields
external table
Tables and data are separate
links
The \t delimiter is best designed to be
flattering
There is an external table, but the data is useless,
we can upload the data into it
Existing table with data
Tables and data are independent and not related.
First create the data
and then build the table, it links to
hive and will actively link and associate tables and data
Anyway, that is to say, the external table and data are independent
Deleting a table does not affect the data itself, it just removes the association.
alter table 表名字 set tblproperties('EXTERNAL'='TRUE/FALSE');
true就是外部
false就是内部
No lowercase,
only uppercase
hive data loading and exporting
local is Linux local
coverage data
Check data from Table 2 and insert into Table 1
Ordinary insert
can be overwritten
, so to speak,
from file to table,
from table to table,
two ways of data loading
It’s just that the direction of importing data is opposite
to that of exporting to different places, and the words are different.
Summarize
提示：重要经验：
1)
2) Learn oracle well, even if the economy is cold, the whole test offer is definitely not a problem! At the same time, it is also the only way for you to test the public Internet police.
3) When seeking AC in the written test, space complexity may not be considered, but the interview must consider both the optimal time complexity and the optimal space complexity.