hive內表和外表的創建、載入數據、區別

創建表

創建內表

create table customer(
    customerId int,
    firstName string,
    lastName STRING,
    birstDay timestamp
) row format delimited fields  terminated by ','

創建外表

CREATE EXTERNAL table salaries(
    gender string,
    age int ,
    salary DOUBLE,
    zip int 
)row format delimited fields  terminated by ',' LOCATION '/user/train/salaries/';

載入數據

load DATA LOCAL inpath '/root/user/customer.txt' overwrite into table customer;
load DATA LOCAL inpath '/root/user/salaries.txt' overwrite into table salaries;

查看文本數據

[root@centos172 user]# cat /root/user/customer.txt
1,f,jack,,
2,f,luccy,,
[root@centos172 user]# cat /root/user/salaries.txt
male,21,10000,1
female,22,12000,2

查看數據庫數據

hive> desc customer;
OK
customerid              int
firstname               string
lastname                string
birstday                timestamp
Time taken: 0.053 seconds, Fetched: 4 row(s)
hive> desc salaries;
OK
gender                  string
age                     int
salary                  double
zip                     int
Time taken: 0.041 seconds, Fetched: 4 row(s)
hive> select * from customer;
OK
1       f       jack    NULL
2       f       luccy   NULL
Time taken: 0.067 seconds, Fetched: 2 row(s)
hive> select * from salaries;
OK
male    21      10000.0 1
female  22      12000.0 2
Time taken: 0.066 seconds, Fetched: 2 row(s)
hive>

區別

因為我hive也是剛開始了解，所以只講一部分
1.內表主要放在hdfs中默認的hive目錄。外表指定了location
2.刪除內表，重新創建一個一樣的內表，數據不會裝載
刪除外表，重新創建一個一樣的外表，數據會自動的裝載
刪除外表的操作如下

hive> drop table salaries;
OK
Time taken: 0.092 seconds
hive> select * from salaries;
FAILED: SemanticException [Error 10001]: Line 1:14 Table not found 'salaries'
hive> show tables;
OK
customer
Time taken: 0.035 seconds, Fetched: 1 row(s)
hive> CREATE EXTERNAL table salaries(
    >     gender string,
    >     age int ,
    >     salary DOUBLE,
    >     zip int
    > )row format delimited fields  terminated by ',' LOCATION '/user/train/salaries/';
OK
Time taken: 0.058 seconds
hive> show tables;
OK
customer
salaries
Time taken: 0.025 seconds, Fetched: 2 row(s)
hive> select * from salaries;
OK
male    21      10000.0 1
female  22      12000.0 2
Time taken: 0.058 seconds, Fetched: 2 row(s)
hive>

區別1的：
內表的默認路徑

指定外表的路徑如圖：

hive是什么

我當前接觸到就是：
1.把hdf文件具體為table
2.用來查詢，類似sql語句處理