Hive基本命令整理

问题导读
1、如何加载分区表数据？
2、Hive中如何查询使用多少个MapReduce作业 ？
3、查看数组、map、结构？




创建表：

 hive> CREATE TABLE pokes (foo INT, bar STRING);         
Creates a table called pokes with two columns, the first being an integer and the other a string
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创建一个新表，结构与其他一样

hive> create table new_table like records;
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创建分区表：

hive> create table logs(ts bigint,line string) partitioned by (dt String,country String);
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加载分区表数据：

hive> load data local inpath '/home/hadoop/input/hive/partitions/file1' into table logs partition (dt='2001-01-01',country='GB');
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展示表中有多少分区：

hive> show partitions logs;
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展示所有表：

hive> SHOW TABLES;         
lists all the tables hive> SHOW TABLES '.*s';

lists all the table that end with 's'. The pattern matching follows Java regular expressions. Check out this link for documentation http://java.sun.com/javase/6/docs/api/java/util/regex/Pattern.html
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显示表的结构信息

hive> DESCRIBE invites;         
shows the list of columns
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更新表的名称：

hive> ALTER TABLE source RENAME TO target;
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添加新一列

 hive> ALTER TABLE invites ADD COLUMNS (new_col2 INT COMMENT 'a comment');   
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删除表：

 hive> DROP TABLE records; 
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删除表中数据，但要保持表的结构定义

 hive> dfs -rmr /user/hive/warehouse/records;
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从本地文件加载数据：

hive> LOAD DATA LOCAL INPATH '/home/hadoop/input/ncdc/micro-tab/sample.txt' OVERWRITE INTO TABLE records;
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显示所有函数：

 hive> show functions;
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查看函数用法：

 hive> describe function substr;
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查看数组、map、结构

hive> select col1[0],col2['b'],col3.c from complex;
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内连接：

 hive> SELECT sales.*, things.* FROM sales JOIN things ON (sales.id = things.id);
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查看hive为某个查询使用多少个MapReduce作业

hive> Explain SELECT sales.*, things.* FROM sales JOIN things ON (sales.id = things.id);
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外连接：

hive> SELECT sales.*, things.* FROM sales LEFT OUTER JOIN things ON (sales.id = things.id); hive> SELECT sales.*, things.* FROM sales RIGHT OUTER JOIN things ON (sales.id = things.id); hive> SELECT sales.*, things.* FROM sales FULL OUTER JOIN things ON (sales.id = things.id);
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in查询：Hive不支持，但可以使用LEFT SEMI JOIN

hive> SELECT * FROM things LEFT SEMI JOIN sales ON (sales.id = things.id);
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Map连接：Hive可以把较小的表放入每个Mapper的内存来执行连接操作

hive> SELECT /*+ MAPJOIN(things) */ sales.*, things.* FROM sales JOIN things ON (sales.id = things.id);
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INSERT OVERWRITE TABLE ..SELECT：新表预先存在

hive> FROM records2     > INSERT OVERWRITE TABLE stations_by_year SELECT year, COUNT(DISTINCT station) GROUP BY year     
> INSERT OVERWRITE TABLE records_by_year SELECT year, COUNT(1) GROUP BY year     
> INSERT OVERWRITE TABLE good_records_by_year SELECT year, COUNT(1) WHERE temperature != 9999 AND (quality = 0 OR quality = 1 OR quality = 4 OR quality = 5 OR quality = 9) GROUP BY year;  
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CREATE TABLE ... AS SELECT：新表表预先不存在

hive>CREATE TABLE target AS SELECT col1,col2 FROM source;
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创建视图：

hive> CREATE VIEW valid_records AS SELECT * FROM records2 WHERE temperature !=9999;
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查看视图详细信息：

 hive> DESCRIBE EXTENDED valid_records;
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谢谢楼主分享，原来hive可以创建视图，这个不清楚，扫盲了 。

hive> Explain SELECT sales.*, things.* FROM sales JOIN things ON (sales.id = things.id);

这个怎么查看使用多少个MapReduce作业