How to calculate Date difference in Hive

Question

I\'m a novice. I have a employee table with a column specifying the joining date and I want to retrieve the list of employees who have joined in the last 3 months. I understand

Answer 1

If you need the difference in seconds (i.e.: you're comparing dates with timestamps, and not whole days), you can simply convert two date or timestamp strings in the format 'YYYY-MM-DD HH:MM:SS' (or specify your string date format explicitly) using unix_timestamp(), and then subtract them from each other to get the difference in seconds. (And can then divide by 60.0 to get minutes, or by 3600.0 to get hours, etc.)

Example:

UNIX_TIMESTAMP('2017-12-05 10:01:30') - UNIX_TIMESTAMP('2017-12-05 10:00:00') AS time_diff -- This will return 90 (seconds). Unix_timestamp converts string dates into BIGINTs. 

More on what you can do with unix_timestamp() here, including how to convert strings with different date formatting: https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF#LanguageManualUDF-DateFunctions