HIVE基础操作（命令，表，数据导出导入等）--持续更新

1.show databases;
2.show tables;
3.show tables in 数据库名;(不在对应数据库下可查到想要的表名)
4.show tables in hive 'tom*'; 查询在hive数据库下，tom开头的表名。
5.desc extended tablename; 
可以查看表详细信息，其中tableType=MANAGED_TABLE或EXTENDED_TATBLE 看出是内部表还是外部表
6.数据库的增删改
(1)创建
create database if not exists hive;
使用if not exists 可以避免抛出错误信息。
(2)删除数据库
drop database if exists hive;
if exists 是可选的，如果加了这个子句，避免hive不存在抛出的异常。

默认情况，hive是不允许删除一个带有表的数据库的。用户可以先清空数据库表，再删除库，或者使用关键字cascade：
drop database if exists hive cascade;

(3)修改数据库
可以修改数据库的dbproperties,设置键值对属性值，但是其他元数据信息是不能修改的。如：
alter database hive set dbproperties(‘edited-by’=’wang’);
alter database mytest set dbproperties('creator'='wangdd');

7.创建表
(1)基本语法
CREATE [TEMPORARY（临时表）] [EXTERNAL（外部表，如果不加该关键字就是创建内部表）] TABLE [IF NOT EXISTS] [db_name.]table_name   
[(col_name data_type [COMMENT col_comment]（列的注释）, ... [constraint_specification])]
[COMMENT table_comment]（表的注释）

  [PARTITIONED BY （分区）(col_name data_type [COMMENT col_comment], ...)]
  [CLUSTERED BY（分布） (col_name, col_name, ...) [SORTED BY (col_name [ASC|DESC], ...)] INTO num_buckets BUCKETS（分桶）]
  [SKEWED BY (col_name, col_name, ...) -- (Note: Available in Hive 0.10.0 and later)]
     ON ((col_value, col_value, ...), (col_value, col_value, ...), ...)
     [STORED AS DIRECTORIES]
  [
   [ROW FORMAT row_format] 分隔符的指定
   [STORED AS file_format] 数据存储格式
     | STORED BY 'storage.handler.class.name' [WITH SERDEPROPERTIES (...)]  -- (Note: Available in Hive 0.6.0 and later)
  ]
  [LOCATION hdfs_path]真实数据存放的位置
  [TBLPROPERTIES (property_name=property_value, ...)]   -- (Note: Available in Hive 0.6.0 and later)
  [AS select_statement];   -- (Note: Available in Hive 0.5.0 and later; not supported for external tables) 


create table hive.person(
id int,
name string,
likes array,
desc map
desc struct

)
ROW FORMAT  DELIMITED FIELDS TERMINATED BY ','
COLLECTION ITEMS TERMINATED BY '-'
LINES TERMINATED BY '\n'
NULL DEFINED AS '@' --在显示的时候就是null了
STORED AS TEXTFILE;

(2)复制一个表结构（不包含数据）
CREATE [TEMPORARY] [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.]table_name
  LIKE existing_table_or_view_name
  [LOCATION hdfs_path];
  CREATE TABLE like_student LIKE student;
(3)通过查询来创建另外一张表
CREATE TABLE new_key_value_store
   ROW FORMAT SERDE "org.apache.hadoop.hive.serde2.columnar.ColumnarSerDe"
   STORED AS RCFile
   AS
SELECT (key % 1024) new_key, concat(key, value) key_value_pair
FROM key_value_store
SORT BY new_key, key_value_pair;

  CREATE TABLE s_person1
  ROW FORMAT DELIMITED FIELDS TERMINATED BY '#'
  COLLECTION ITEMS TERMINATED BY '^'
  MAP KEYS TERMINATED BY '_'
  NULL DEFINED AS '@'
  AS SELECT * FROM person1;

（4）分区表
create table hive.tomcat_log(
id string,
page string,
status int,
traffic int
)
partitioned by (year string,month string,day string)
ROW FORMAT  DELIMITED FIELDS TERMINATED BY ',' 
STORED AS TEXTFILE; 

（5）分桶表
create table clus2(
cc int)
CLUSTERED BY (cc)
SORTED by (cc)
into 3 buckets; 

8.数据的导入
(1)LOAD DATA 
LOAD DATA [LOCAL] INPATH 'filepath' [OVERWRITE]（覆盖，不写就是追加） INTO TABLE tablename [PARTITION (partcol1=val1, partcol2=val2 ...)]

在本地导入（Linux系统下）复制的过程
load data local inpath '/home/wangfutai/a/1.txt'  INTO TABLE hive.union_test;

在hdfs导入（hdfs系统下）剪切的过程，原来目录数据没了
追加：
load data inpath '/user/wangfutai/hive/warehouse/hive.db/st/st.txt'  INTO TABLE hive.union_test;
覆盖：
load data inpath '/user/wangfutai/hive/warehouse/hive.db/st/1.txt' OVERWRITE INTO TABLE hive.union_test;
(2)分区表的导入
静态模式：
load data local inpath '/home/wangfutai/a/2.txt' OVERWRITE  INTO TABLE hive.tomcat_log PARTITION(year='2017',month='11',day='5');

load data  inpath '/user/wangfutai/mr/ETLOutPut16/part-r-00001' OVERWRITE  INTO TABLE hive.tomcatelog PARTITION(days='20170531');

动态模式：
覆盖模式：只会覆盖相同分区数据,其他分区不受影响·
INSERT OVERWRITE TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...) [IF NOT EXISTS]] select_statement1 FROM from_statement;
追加模式：
INSERT INTO TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...)] select_statement1 FROM from_statement;
例子：
INSERT OVERWRITE TABLE  dynamic_human2 PARTITION (sexs) select * from human1;

以下插入，需要human3的列比dynamic_human3 少一列
INSERT OVERWRITE TABLE  dynamic_human3 PARTITION (sexs=‘nan’) select * from human3;


9.数据的导出
(1)通过建表的方式
CREATE TABLE new_key_value_store
   ROW FORMAT SERDE "org.apache.hadoop.hive.serde2.columnar.ColumnarSerDe"
   STORED AS RCFile
   AS
SELECT (key % 1024) new_key, concat(key, value) key_value_pair
FROM key_value_store
SORT BY new_key, key_value_pair;

CREATE TABLE s_person1
ROW FORMAT DELIMITED FIELDS TERMINATED BY '#'
COLLECTION ITEMS TERMINATED BY '^'
MAP KEYS TERMINATED BY '_'
NULL DEFINED AS '@'
AS SELECT * FROM person1;

(2)通过insert 
INSERT OVERWRITE [LOCAL] DIRECTORY directory1
[ROW FORMAT row_format] [STORED AS file_format] 
SELECT ... FROM ...
  保存到本地
  INSERT OVERWRITE LOCAL DIRECTORY
'/home/wangfutai/a/partition_data'
  ROW FORMAT DELIMITED FIELDS TERMINATED BY '#'
  NULL DEFINED AS '@'
  SELECT * FROM st;

 保存到hdfs中  会覆盖掉原来目录
  INSERT OVERWRITE  DIRECTORY
 '/user/candle/hive_data/person1_data'
  ROW FORMAT DELIMITED FIELDS TERMINATED BY '#'
  COLLECTION ITEMS TERMINATED BY '^'
  MAP KEYS TERMINATED BY '_'
  NULL DEFINED AS '@'
  SELECT * FROM person1;

（3）通过查询插入表中，指定列作为分区
覆盖模式：只会覆盖相同分区数据,其他分区不受影响·
INSERT OVERWRITE TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...) [IF NOT EXISTS]] select_statement1 FROM from_statement;
追加模式：
INSERT INTO TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...)] select_statement1 FROM from_statement;
覆盖：
INSERT OVERWRITE TABLE dynamic_human1 PARTITION(sex) SELECT * FROM human1;
追加:
INSERT INTO TABLE dynamic_human1 PARTITION(sex) SELECT * FROM human2;

也可以在插入的时候 指定分区列名,但是指定了分区列名,那么human3就必须没有sex这列，因为sex分区已经指定了

INSERT OVERWRITE TABLE dynamic_human1 PARTITION(sex='aaa') SELECT * FROM human1;