Hive slide，

Hive slide，

•数据仓库， •把类似SQL的语法转化成MapReduce程序 •不支持Index,Transaction,分钟级别的延时 •不支持SQL的Having •数据类型支持 –基本类型string,int,double,boolean等

–复杂类型的Array,Map,Struct

 

 

•%export HIVE_HOME=/home/my/hive •运行：bin/hive •hive>SHOW TABLES; •hive-f script.q •hive-e 'SELECT * FROM dummy'

 

 

 

 

•建表 •CREATETABLErecords –(year STRING,temperature INT, quality INT) –ROWFORMAT DELIMITED –  FIELDS TERMINATED BY '\t'; •从文件载入： –LOADDATALOCAL INPATH 'input/ncdc/micro-tab/sample.txt' –OVERWRITEINTO TABLE records

 

 

 

Errorwhile making MR scratch directory :

•把hadoop的配置文件core-site.xml中的： •fs.default.name里的值改成hosts里的名称 •然后重启hadoop和hive •如果提示namenode is in safe mod –hadoop dfsadmin -safemode leave –或在hdfs上建立相关目录并加权限 –%hadoop fs -mkdir /tmp –%hadoop fs -chmod a+w /tmp –%hadoop fs -mkdir/user/hive/warehouse –%hadoop fs -chmod a+w/user/hive/warehouse

 

 

•托管表会移动数据到Hive的数据仓库目录 –CREATETABLE managed_table(dummy STRING); –LOADDATA INPATH '/user/tom/data.txt' INTO table managed_table; •外部表： –CREATEEXTERNALTABLE external_table(dummy STRING)LOCATION '/user/tom/external_table'; –LOADDATA INPATH '/user/tom/data.txt' INTO TABLE external_table; –删除外部表的时候不会删除数据，只删除metaata

 

 

 

•CREATETABLE bucketed_users (idINT, name STRING) •CLUSTEREDBY (id) INTO 4 BUCKETS; •分隔成4片，用于拆分成多个MapReduce任务

 

 

 

 

 

•selectmyFun(age)from tab3; •publicclass MyFunextends UDF { •} •编写完以后注册： –createtemporary function myFun as 'com.MyFun'