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Saturday, January 4, 2014

Redshift convert integer to Timestamp type and convert epoch time to timestamp on the fly

Currently, Redshift does not support to_timestamp function, which is convenient for converting String or Integer into Timestamp format. Below is a quick notes on how to convert String or integer to be timestamp in Redshift.
Simple, using substring function to get parts for Year, Month, Date, Hour, Minute, Second from String or Integer and concatenate them into Timestamp format and cast to timestamp. Below are examples,
Suppose Table t1 has a column (col1) have integer value in pattern YYMMDDhhmm. For example, it value is 0403051030. It means Year 2014, March fifth, and thirty minutes past ten o'clock. We can use below two methods to convert it to be Timestamp value.
cast(('20' || substring(col1,1, 2) || substring(col1,3, 2) || 
      substring(col1,5, 2) || ' ' || substring(col1,7, 2) || ':' 
      || substring(col1,9, 2)) as timestamp) 
FROM t1;

cast(to_date(col1, 'YYMMDD') || ' ' 
    || substring(col1,7,2) || ':' 
|| substring(col1,9,2) as timestamp) 
FROM t1;
Also, get idea from a blog about how to convert epoch time to timestamp on fly in Redshift.

    (TIMESTAMP 'epoch' + myunixtime * INTERVAL '1 Second ') 
AS   mytimestamp 

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