Internal and external table operations, hive data export and import operations

create database review01;
use review01;
-- 1. Operation of internal and external tables
--1. Internal table operations
--Three ways to create:
create table stu(id int,name string);
insert into stu values ​​(1,'Zhang San');
create table stu1 like stu;
create table stu2 as select * from stu;
--Delete internal tables
drop table stu2;
--View internal table structure
desc formatted stu;
--Clear table data
truncate table  stu1;
--2. Operation of external tables, note: external tables cannot be created and deleted using as, because there is no absolute control over the data.
--Two ways to create
create EXTERNAL table pp(id int,name string);
create EXTERNAL table pp1 like pp;
--Delete external table
drop table pp1;
--View external table structure
desc formatted pp;
--2. View table and modify table
--1.View table
show databases;--View all tables
show create table pp;--View table creation statements
desc pp;--View table information
desc formatted pp;--View table structure
--2. Modify the table
alter table pp rename to ps;--modify table name
alter table ps set location 'storage path in hdfs';--Modify the storage path of the table. If the path does not exist, it will be created when inserting data
alter table ps set tblproperties ('c'='v');--Modify table properties
alter table ps set tblproperties ('EXTERNAL'='FALSE');--Change external table to internal table
alter table stu1 set tblproperties ('EXTERNAL'='TRUE'); --change internal table to external table
alter table ps add columns (pid int);--Add fields
alter table stu replace columns (id int,name varchar(100));--Replace fields
alter table ps change pid product string;--change field name
--3. Default delimiter and specified delimiter and quick mapping table
--The default delimiter is generally /0001,□,SOH
create table tz(
    dt string,id string,name string,url string
) row format delimited fields terminated by '\t';--specify delimiter
load data inpath '/search_log.txt' into table tz;--Quickly load the table, the essence is to move, the original file will disappear
select * from tz limit 5;--verification table
-- 4. Import and export of Hive data
--import/load
load data local inpath '/search_log.txt' into table tz1;--Import from linux to hive table, the original file is retained
load data inpath '/user/hive/warehouse/review01.db/tz2'
    overwrite into table tz3;--When importing from one hdfs table to another, the original data will disappear and the data in the new table will be overwritten.
insert into table tz select * from tz1;--load data from other tables
insert overwrite table tz3 select * from tz1;--overwrite and load data from other tables
--export
insert overwrite local directory '/home' select * from tz;--Export from hive to linux, default separator, ensure the directory is empty
insert overwrite local directory '/home'
row format delimited fields terminated by '-' select * from tz;--Specify delimiter
insert overwrite directory '/output'
    row format delimited fields terminated by '/' select * from tz;--Export from hive to hdfs
--bin/hive -e "select * from myhive.test_load;" > /home/hadoop/export3/export4.txt--Input and export hive data in linux
--bin/hive -f export.sql > /home/hadoop/export4/export4.txt --script output