You have marks of all the students of a class with roll number in CSV file, It is needed to calculate the percentage of each student in hive.
Download the sample CSV file marks which have 7 columns, 1st column is Roll no and other 6 columns are subject1 subject2….subject6.
Step 1: Loading the sample CSV file marks.csv into Hive Table.
I have Local directory named as “calculate-percentage-in-hive” in path “/root/local_bdp/problems/”
So I have kept marks.csv file in that path.
You can see sample data in below screen shot:-
Let’s create HDFS directory using below command
hadoop fs -mkdir -p hdfs://sandbox.hortonworks.com:8020/user/root/bdp/problems/cal_per_hive/ip/
As you can see “ip” directory is created for input files.
Now we can load file into HDFS using below command
hadoop fs -put /root/local_bdp/problems/calculate-percentage-in-hive/marks.csv hdfs://sandbox.hortonworks.com:8020/user/root/bdp/problems/cal_per_hive/ip/
If you have trouble understanding loading of csv file in to hive you can refer here.Use below commands in hive to create an external table.
CREATE SCHEMA IF NOT EXISTS bdp; CREATE EXTERNAL TABLE IF NOT EXISTS bdp.hv_per (roll_no INT,subject1 INT,subject2 INT,subject3 INT,subject4 INT,subject5 INT,subject6 INT) ROW FORMAT DELIMITED FIELDS TERMINATED BY ',' STORED AS TEXTFILE LOCATION 'hdfs://sandbox.hortonworks.com:8020/user/root/bdp/problems/cal_per_hive/ip/';
You can skip above steps if data is already available in hive table.
Step 2 : Hive
Now it’s time to interact with hive CLI.
Enter the below command:-
It will take you to hive CLI.As we have created a hv_per table in bdp schema.Which have all 7 columns.Use below command to see whether data is loaded or not.
- Select * FROM bdp.hv_per;
Step 3: Calculation of Percentage
Use below query to calculate percentage .
- SELECT roll_no,CAST(subject1+subject2+subject3+subject4+subject5+subject6 AS float)/6.0 AS percentage
- FROM bdp.hv_per;
As you can see first we are summing all subjects and then casting the result of the sum in to float, after that we are dividing it by 6.0, As we have assumed that total marks of each subject are 100.you can change the formula if you wish.
Refer below screen shot. Which is the output of the query.
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