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Handling the NULL data in impala

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Handling the NULL data in impala

New Contributor

I am trying understand the behavior of arithmetic operation in impala

i am using the following table


║ id     name   salary 
╠══╬════╬════╣
║ 1       cde      5636 
║ 2       asd      148    
║ 3       pwe      null    
║ 4       lmn       959    

when i execute the following query

 

select salary+20 as sum1 from table where id=3;
it returns me

 

    |sum1
---|-----
1 |NULL

when i run sum on the column with

 

select sum(salary) as sum1 from table;

 

    |sum1
---|-----
1 |6743

 

I am unable to understand how same arithmetic operations are behaving differently