Converting ISO Dates to Text Representations in SQL

This is more for my own benefit than for anyone else, but I can see this question cropping up a few more times over the next few months. The issue is that I have a table containing an ISO date and have to populate a legacy table in which the date is represented as a ten character string (YYYY-MM-DD).

This works:

select trim(char(year(iso_date))) || '-' ||
       substr(digits(month(iso_date)), 9, 2) || '-' ||
       substr(digits(char(day(iso_date))), 31, 2)
from ...

The digits function returns a fixed-length character-string representation of the absolute value of a number. then all you need to do is identify the bit of the string that you need to use.

5 thoughts on “Converting ISO Dates to Text Representations in SQL

  1. If it’s the || symbols that caused that caused the question, these are concatenation tokens. They’re not standard SQL, but very handy when you have more than two strings to concatenate.

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  2. Ah. Fair Enough. There’s T-SQL functions that make this easier. I work with a DB whizz and he’s got all kinds of good stuff for dealing with the knottiest string parsing/date conversion challenges.

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  3. Thanks for the thought. DB2 is pretty good at date handling – the problem is that whoever wrote the (soon th be gone) legacy application managed to avoid using any of this functionality at all.

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