Hive(七):HQL DML

• HQL DML 主要涉到对Hive表中数据操作，包含有：load、INSERT、DELETE、EXPORT and IMPORT，详细资料参见：https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DML

目录：

• Loading files into tables
• Inserting data into Hive Tables from queries
• Writing data into the filesystem from queries
• Inserting values into tables from SQL
• Delete
• 应用Demo

 Loading files into tables：

---

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

  #创建表
  CREATE TABLE web_log(viewTime INT, userid BIGINT, url STRING, referrer STRING, ip STRING)
  ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t';
  
  #导入文件数据
  LOAD DATA LOCAL INPATH '/usr/zhu/table.txt'  OVERWRITE INTO TABLE web_log;

• OVERWRITE:

1. 目标表（或者分区）中的内容（如果有）会被删除，然后再将 filepath 指向的文件/目录中的内容添加到表/分区中
2. 如果目标表（分区）已经有一个文件，并且文件名和 filepath 中的文件名冲突，那么现有的文件会被新文件所替代

Inserting data into Hive Tables from queries:

---

• 语法：INSERT OVERWRITE TABLE tablename1 [PARTITION] select_statement1 FROM from_statement;
           INSERT INTO TABLE tablename1 [PARTITION] select_statement1 FROM from_statement;
• 示例代码：

  #创建结构相同的表
  create table empDemo as employee;
  
  #插入数据
  insert into table empDemo select * from employee;
  
  #覆盖插入数据
  insert overwrite table empDemo select * from employee;

Writing data into the filesystem from queries:

---

• 语法：INSERT OVERWRITE [LOCAL] DIRECTORY directory1 SELECT ... FROM ...
• 示例代码：

  INSERT OVERWRITE LOCAL DIRECTORY './tmp/zhu'  SELECT * FROM employee;

Inserting values into tables from SQL：

---

• 语法：INSERT INTO TABLE tablename VALUES values_row [, values_row ...]

示例代码：

#单行插入
insert into table employee values('','','tgzhu');

#多行插入
insert into table employee values('','','WangWu'),('','','ZhaoZhao');

Delete：

---

• 语法：DELETE FROM tablename [WHERE expression]

应用Demo:

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• 以一个实际的应用Demo对Hive 的 DDL、DML 进行说明，过程如下
• 创建与HBase关联的外部表，HQL如下：

  CREATE EXTERNAL TABLE if not exists Hive_CM_EvcRealTimeData(
           Rowkey  string,
           RealTimeData_CarNo  string,
           RealTimeData_Time  string,
       RealTimeData_Speed decimal(20,8),
       RealTimeData_Mileage decimal(20,8),
       RealTimeData_HighestVoltageBatteryOrd int,
       RealTimeData_Latitude decimal(20,8),
       RealTimeData_Longitude decimal(20,8)
    )
   STORED BY 'org.apache.hadoop.hive.hbase.HBaseStorageHandler'
   WITH SERDEPROPERTIES('hbase.columns.mapping' = ':key,d:RealTimeData_CarNo, ata_Time,d:RealTimeData_Speed,d:RealTimeData_Mileage,d:RealTimeData_HighestVoltageBatteryOrd,d:RealTimeData_Latitude,d:RealTimeData_Longitude')
   TBLPROPERTIES('hbase.table.name' = 'CM_EvcRealTimeData')

• 创建一个用来保存计算结果的hive实表，如下：

CREATE TABLE if not exists Hive_CM_CarDailyRpt(
         CarNo        string,
         DTime        string,
     OnLineCount  int,
         RunCount     int,
     Mileage      decimal(20,8),
         MaxSpeed     decimal(20,8),
     totalPower   decimal(20,8),
     AverageSpeed decimal(20,8),
     CDI_BatteryFlag string,
     CDI_CoordinatorFlag string
  )
  STORED AS TEXTFILE

• 计算并将结果插入实表，如下：

set hive.execution.engine = tez;

Insert overwrite table Hive_CM_CarDailyRpt
select
      CarNo,DTime,
      CONVERT(int,SUM(CT)) as OnLineCount ,
      CONVERT(int,SUM(CTSPEED)) as RunCount,
      CONVERT(decimal(18,2),MAX(MILE)-MIN(MILE)) as Mileage ,
      CONVERT(decimal(18,2),MAX(SPEED)) as MaxSpeed,
      ((MAX(MILE)-MIN(MILE))*0.2) as totalPower,
      case when SUM(CTSPEED)>0 then CONVERT(decimal(18,2),((MAX(MILE)-MIN(MILE))/SUM(CTSPEED)))
      else 0 end as AverageSpeed,
      case when SUM(RealTimeData_HighestVoltageBatteryOrd)>0 then '' else '' end as BatteryFlag,
      case when (SUM(RealTimeData_Latitude) + SUM(RealTimeData_Longitude)) >0 then '' else '' end as LatitudeFlag,
 from
    (
     SELECT REALTIMEDATA_CARNO AS CARNO,
          substring(RealTimeData_Time,1,8) as DTime,
          1 AS CT,
          CASE WHEN REALTIMEDATA_SPEED>0 THEN 1 ELSE 0 END AS CTSPEED,
          CASE WHEN REALTIMEDATA_MILEAGE=0 THEN NULL ELSE REALTIMEDATA_MILEAGE END AS MILE,
          CASE WHEN REALTIMEDATA_SPEED>200 then 0 else REALTIMEDATA_SPEED end AS SPEED,
          RealTimeData_HighestVoltageBatteryOrd,
          RealTimeData_Latitude,RealTimeData_Longitude
          FROM CM_EvcRealTimeData
      ) t
 group by CarNo,DTime

• 再将计算结果转存关系型数据库或HBase