How to calculate Date difference in Hive

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梦如初夏
梦如初夏 2021-02-01 04:17

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

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  • 2021-02-01 05:04

    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

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  • 2021-02-01 05:06
    datediff(to_date(String timestamp), to_date(String timestamp))
    

    For example:

    SELECT datediff(to_date('2019-08-03'), to_date('2019-08-01')) <= 2;
    
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  • 2021-02-01 05:07

    yes datediff is implemented; see: https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF

    By the way I found this by Google-searching "hive datediff", it was the first result ;)

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  • 2021-02-01 05:13

    I would try this first

    select * from employee where month(current_date)-3 = month(joining_date)
    
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