Date functions in Teradata

I have teradata scripts

AND ADD_MONTHS('?StartDate',1)-1 BETWEEN A.CNTSTRT_DT AND COALESCE(A.CNTEND_DT, DATE) 

This script looks like it prompts for a date, then adds one month to that date. But I'm not clear on what the -1 does.

Additionally, I see that it compares the date to see if they are between the CNTSTRT_DT and CNTEND_DT, but what does the DATE do specifically?

1 Answer

The -1 is to substruct one day, for example the query:

select ADD_MONTHS(cast('2016/01/25' as date),1)-1 

returns: 24/02/2016

Also, "Date" is a function which returns current date.