【Hadoop】Hive HSQ 使用 && 自定义HQL函数

4 HQL

4.1 官网

4.1.1 https://cwiki.apache.org/confluence/display/Hive/LanguageManual

4.1.2 性能调优

4.1.2.1 Explain Execution Plan

4.1.2.2 https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Explain

4.2 示例

4.2.1 增加分区

4.2.1.1 alter table tab_ip change id id_alter string; ALTER TABLE tab_cts ADD PARTITION (partCol = 'dt') location '/external/hive/dt';

4.2.2 结果写到HDFS

4.2.2.1 insert overwrite local directory './hivetest/' select * from tbl_order_pt where month='201602'; insert overwrite directory '/hivetest/' select * from tbl_order_pt where month='201602';

4.2.3 集合类型字段

4.2.3.1 ARRAY

4.2.3.1.1 create table tab_array(a array<int>,b array<string>) row format delimited fields terminated by '\t' collection items terminated by ','; //示例数据 tobenbrone,laihama,woshishui 13866987898,13287654321 abc,iloveyou,itcast 13866987898,13287654321 //操作 select a[0] from tab_array; select * from tab_array where array_contains(b,'word'); insert into table tab_array select array(0),array(name,ip) from tab_ext t;

4.2.3.2 MAP

4.2.3.2.1 create table tab_map(name string,info map<string,string>) row format delimited fields terminated by '\t' collection items terminated by ';' map keys terminated by ':'; //示例数据： fengjie age:18;size:36A;addr:usa furong age:28;size:39C;addr:beijing;weight:180KG //操作 load data local inpath '/home/hadoop/hivetemp/tab_map.txt' overwrite into table tab_map; insert into table tab_map select name,map('name',name,'ip',ip) from tab_ext;

4.2.3.3 STRUCT

4.2.3.3.1 create table tab_struct(name string,info struct<age:int,tel:string,addr:string>) row format delimited fields terminated by '\t' collection items terminated by ',' //操作 load data local inpath '/home/hadoop/hivetemp/tab_st.txt' overwrite into table tab_struct; insert into table tab_struct select name,named_struct('age',id,'tel',name,'addr',country) from tab_ext;

4.2.4 自定义函数

4.2.4.1 select if(id=1,first,no-first),name from tab_ext; hive>add jar /home/hadoop/myudf.jar; hive>CREATE TEMPORARY FUNCTION my_lower AS 'org.dht.Lower'; select my_upper(name) from tab_ext;

4.2.5 高级查询

4.2.5.1 select * from tbl_order_pt where month='201602' sort by id desc limit 0,3; select a.ip,b.book from tab_ext a join tab_ip_book b on(a.name=b.name);

4.2.6 HQL CLI

4.2.6.1 hive -S -e 'select country,count(*) from tab_ext' > /home/hadoop/hivetemp/e.txt 有了这种执行机制，就使得我们可以利用脚本语言（bash shell,python）进行hql语句的批量执行，示例如下： hive -S -e 'use db_order;select * from tbl_order_pt where month='201602' sort by id desc limit 0,3;' > result.txt

 

自定义函数示例代码：

package cn.itcast.bigdata;

import java.util.HashMap;

import org.apache.hadoop.hive.ql.exec.UDF;

public class PhoneNbrToArea extends UDF{

    private static HashMap<String, String> areaMap = new HashMap<>();
    static {
        areaMap.put("", "beijing");
        areaMap.put("", "tianjin");
        areaMap.put("", "nanjing");
    }

    //一定要用public修饰才能被hive调用
    public String evaluate(String pnb) {

        String result  = areaMap.get(pnb.substring(,))==null? (pnb+"    huoxing"):(pnb+"  "+areaMap.get(pnb.substring(,)));        

        return result;
    }

}