Hive详解之DML(Data Manipulation Language)

　　DML主要是对Hive 表中的数据进行操作的（增 删 改），但是由于Hadoop的特性，所以单条的修改、删除，其性能会非常的低所以不支持进行级操作； 

主要说明一下最常用的批量插入数据较为常用的方法：

1、从文件中加载数据

语法：LOAD DATA [LOCAL] INPATH 'filepath' [OVERWRITE] INTO TABLE tablename [PARTITION (partcol1=val1, partcol2=val2 ...)]

　例：load data local inpath '/opt/data.txt' overwrite into table table1; -- 如果文件存放在HDFS中，则不需要写Local

2、从其他表中插入数据

语法：Standard syntax:
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;

例：

from psn INSERT OVERWRITE TABLE psn01 SELECT *
或者
INSERT OVERWRITE TABLE psn01 SELECT * from psn;
或者
from psn ppp
INSERT OVERWRITE TABLE psn01
SELECT ppp.id, ppp.name, 28,ppp.likes, ppp.address;

补充：

1. DDL（Data Definition Languages）语句：即数据库定义语句，用来创建数据库中的表、索引、视图、存储过程、触发器等，常用的语句关键字有：CREATE,ALTER,DROP,TRUNCATE,COMMENT,RENAME。
2. DML（Data Manipulation Language）语句：即数据操纵语句，用来查询、添加、更新、删除等，常用的语句关键字有：SELECT,INSERT,UPDATE,DELETE,MERGE,CALL,EXPLAIN PLAN,LOCK TABLE,包括通用性的增删改查。
3. DCL（Data Control Language）语句：即数据控制语句，用于授权/撤销数据库及其字段的权限（DCL is short name of Data Control Language which includes commands such as GRANT and mostly concerned with rights, permissions and other controls of the database system.）。常用的语句关键字有：GRANT,REVOKE。
4. TCL（Transaction Control Language）语句：事务控制语句，用于控制事务，常用的语句关键字有：COMMIT,ROLLBACK,SAVEPOINT,SET TRANSACTION。