本篇主要演示Hive的数据操作，包括向表中装载数据、插入数据、创建表以及导出数据。
一 向表中装载数据
1 语法结构
LOAD DATA [LOCAL] INPATH 'filepath' [OVERWRITE] INTO TABLE tablename [PARTITION (partcol1=val1, partcol2=val2 ...)]
2 示例
hive> load data local inpath '/home/hadoop/emp/'
> into table emp;
Loading data to table hive.emp
OK
Time taken: 0.95 seconds
hive> select *from emp;
OK
emp.id emp.name
1 Alen
2 Jane
3 Tom
4 Peter
Time taken: 0.252 seconds, Fetched: 4 row(s)
hive>
二 通过查询语句向表中插入数据
1 语法结构
INSERT OVERWRITE TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...) [IF NOT EXISTS]] select_statement1 FROM from_statement;
INSERT INTO TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...)] select_statement1 FROM from_statement;
Hive extension (multiple inserts):
FROM from_statement
INSERT OVERWRITE TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...) [IF NOT EXISTS]] select_statement1
[INSERT OVERWRITE TABLE tablename2 [PARTITION ... [IF NOT EXISTS]] select_statement2]
[INSERT INTO TABLE tablename2 [PARTITION ...] select_statement2] ...;
FROM from_statement
INSERT INTO TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...)] select_statement1
[INSERT INTO TABLE tablename2 [PARTITION ...] select_statement2]
[INSERT OVERWRITE TABLE tablename2 [PARTITION ... [IF NOT EXISTS]] select_statement2] ...;
Hive extension (dynamic partition inserts):
INSERT OVERWRITE TABLE tablename PARTITION (partcol1[=val1], partcol2[=val2] ...) select_statement FROM from_statement;
INSERT INTO TABLE tablename PARTITION (partcol1[=val1], partcol2[=val2] ...) select_statement FROM from_statement;
2 示例
hive> create table t_emp(id int , name string);
OK
Time taken: 1.611 seconds
hive> insert overwrite table t_emp
> select *from emp;
hive> select *from t_emp;
OK
t_emp.id t_emp.name
1 Alen
2 Jane
3 Tom
4 Peter
Time taken: 0.296 seconds, Fetched: 4 row(s)
三 单个查询语句中创建表并加载数据
通过Create Table AS实现：
hive> create table t_emp as
> select *from emp;
hive> select *from t_emp;
OK
t_emp.id t_emp.name
1 Alen
2 Jane
3 Tom
4 Peter
Time taken: 0.311 seconds, Fetched: 4 row(s)
四 导出数据
1 语法结构
Standard syntax:
INSERT OVERWRITE [LOCAL] DIRECTORY directory1
[ROW FORMAT row_format] [STORED AS file_format] (Note: Only available starting with Hive 0.11.0)
SELECT ... FROM ...
Hive extension (multiple inserts):
FROM from_statement
INSERT OVERWRITE [LOCAL] DIRECTORY directory1 select_statement1
[INSERT OVERWRITE [LOCAL] DIRECTORY directory2 select_statement2] ...
row_format
: DELIMITED [FIELDS TERMINATED BY char [ESCAPED BY char]] [COLLECTION ITEMS TERMINATED BY char]
[MAP KEYS TERMINATED BY char] [LINES TERMINATED BY char]
[NULL DEFINED AS char] (Note: Only available starting with Hive 0.13)
2 示例
hive> insert overwrite local directory '/home/hadoop/emp'
> select *from emp;
[hadoop@strong ~]$ vim /home/hadoop/emp/000000_0
1^AAlen
2^AJane
3^ATom
4^APeter
注：数据中的列与列之间的分隔符是^A(ascii码是\00001)。
3 使用Hadoop命令导出
[hadoop@strong ~]$ hadoop fs -copyToLocal /user/hive/warehouse/hive.db/emp/ /home/hadoop/
[hadoop@strong ~]$ cat emp/*
1Alen
2Jane
3Tom
4Peter
五 插入值到表中
1 语法结构
Standard Syntax:
INSERT INTO TABLE tablename [PARTITION (partcol1[=val1], partcol2[=val2] ...)] VALUES values_row [, values_row ...]
Where values_row is:
( value [, value ...] )
where a value is either null or any valid SQL literal
2 示例
hive> insert into emp values(5,'Jack'),(6,'Winter');
六 修改操作
1 语法结构
Standard Syntax:
UPDATE tablename SET column = value [, column = value ...] [WHERE expression]
注：update操作仅仅在支持ACID的表上执行。
七 删除操作
1 语法结构
Standard Syntax:
DELETE FROM tablename [WHERE expression]
注：delete操作仅仅在支持ACID的表上执行。
八 合并操作
1 语法结构
Standard Syntax:
MERGE INTO <target table> AS T USING <source expression/table> AS S
ON <boolean expression1>
WHEN MATCHED [AND <boolean expression2>] THEN UPDATE SET <set clause list>
WHEN MATCHED [AND <boolean expression3>] THEN DELETE
WHEN NOT MATCHED [AND <boolean expression4>] THEN INSERT VALUES<value list>
注：merge操作仅仅在支持ACID的表上执行。