An significant part is the treatment of NULL values during data processing and reports. Sometimes it ends up with arithmetic overflow errors or null values if not done properly. There are lots of conditional functions in the Apache Impala that manage NULL values.
- ISNULL
- NVL
- IFNULL
- ZEROIFNULL
The above mentioned four functions does almost the same job. You can use any of them if your data has null values.
SELECT ISNULL(NULL,0)
Returns 0
SELECT NVL(NULL,0)
Returns 0
SELECT IFNULL(NULL,0)
Returns 0
SELECT ZEROIFNULL(0)
Returns 0
ISNULL, IFNULL and NVL are identical and are same in behavior. The ZEROIFNULL function varies marginally from those three functions. The NULL value will be transformed to 0 by this function and nothing more can be achieved.
We’ll learn more about these features in the coming blogs.
Big Data and SQL 
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