标签：des style blog http io ar color os 使用
我们可以使用describe extended financial.employee命令来查看这个表的详细表结构信息（如果当前所处的工作数据库就是financial，那可以不佳finanacial）。hive> describe financial.employee.salary salary float employee salary
create external table if not exists stocks ( exchange string, symbol string, ymd string, price_open float, price_high float, price_low float, price_close float, volume int, price_adj_close float ) row format delimited fields terminated by ',' location '/data/stocks';关键字external告诉hive这个表是外部的，而后面的location子句则用于告诉hive数据位于哪个路径下。
create external table if not exists financial.employee1 like financial.employee location '/path/data'
create table if not exists employee (
name string,
age tinyint,
salary float,
subordinates array<string>,
address struct<city:string,street:string>
)
partitioned by (country string, province string);分区改变了hive对数据存储的组织方式。如果我们是在financial数据库中创建的这个表，那么对于这个表只会有一个employee目录与之对应：hive> set hive.mapred.mode=strict; ... hive> set hive.mapred.mode=nostrict;
hive> show partitions employee; ... country=CN/provice=SHANNXI country=CN/provice=HEBEI ...
hive> show partitions employee partition(country='CN',province='HEBEI'); country=CN/provice=HEBEI
hive> describe extended employee; ... partitionKeys:[FieldSchema(name:country, type:string,comment:null),FieldSchema(name:province, type:string,comment:null)], ...
load data local inpath '$(env:HOME)/hebei-employee' into table employee partition (country = 'CN', province = 'HEBEI');
create external table if not exists log_message( hms int, serverity string, server string, process_id int, message string ) partitioned by (year int, month int, day int) row format delimited fields terminated by '\t';
hive> show partitions log_message; ... year=2014/month=11/day=16 ...
hive> describe extended log_message partition (year=2014, month=11, day=17); ... location:hdfs://master_server/data/log_message/2014/11/17 ...
drop table if exists employee;
alter table log_message rename to logmsg
alter table log_message add if not exists partition(year = 2014, month = 1, day = 1) location '/logs/2014/01/01' partition(year = 2014, month = 1, day = 2) location '/logs/2014/01/02' ...;还可以高效的移动位置来修改某个分区的路径：
alter table log_message partition(year = 2014, month = 1, day = 1) set location 'hdfs://master_server/data/log_message/logs/2014/01/01';用户还可以删除某个分区：
alter table log_message drop if exists partition(year = 2014, month = 1, day = 1);3)修改列信息
alter table log_message change column hms hours_munites_seconds int comment 'THe hours , minutes, and seconds part of the timestamp' after serverity;即使字段名或字段类型没有改变，用户也需要完全指定旧的字段名，并给出新的字段名及新的字段类型。关键字column和comment子句都是可选的。上面的例子将字段转移到了serverity字段之后。如果用户想将这个字段移动到第一个位置，那么只需要使用first关键字替代after other_column子句即可。
alter table log_message add columns ( app_name string comment 'Application name', session_id long comment 'The current session id' );5)删除或替换列
alter table log_message replace columns ( hours_mins_secs int comment 'hour, minute, seconds from timestamp', servertity string comment 'The rest of the message' );这个语句实际上重命名了之前的hms字段并且从之前的表定义的模式中移除了字段server和process_id。因为是alter语句，所以只有表的元数据信息改变了。
alter table log_message set tblproperties ( 'notes' = 'The process id is no longer captured; this column is always NULL' );8)修改存储属性
alter table log_message partition(year = 2014, month = 1, day = 1) set fileformat sequencefilel;
如果表是分区表，那么需要使用partition子句。
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标签：des style blog http io ar color os 使用
原文地址：http://blog.csdn.net/iam333/article/details/41442111
