Skip to Main Content
  • Questions

  • ORA-01722: invalid number error in decode

Breadcrumb

Connor and Chris will both be at AI World from October 12 to October 17 , the premier Oracle conference of 2025. If you're in Vegas, please come say Hi or pop into our sessions

Question and Answer

Chris Saxon

Thanks for the question, BHS.

Asked: October 12, 2017 - 8:31 am UTC

Last updated: October 12, 2017 - 9:44 am UTC

Version: 12c

Viewed 10K+ times! This question is

You Asked

1. select decode('a',1,1,2) from dual --------> O/P Error saying Invalid Number

2. select decode(1,'a',1,2) from dual --------> O/P : 2


what is the difference in the above two cases and also please explain the execution process?


Thanks In Advance.

with LiveSQL Test Case:
https://livesql.oracle.com/apex/f?p=590:1:16775468242205:::::

and Chris said...

As the docs say:

Oracle automatically converts expr and each search value to the data type of the first search value before comparing

http://docs.oracle.com/database/122/SQLRF/DECODE.htm#SQLRF00631

The first search value is the second argument.

So in the first example it sees the value 1. So the database tries to convert 'a' to a number. Which, unsurprisingly, fails.

But in the second example, you have a character ('a'). You can convert all numbers to characters. So it works!



Is this answer out of date? If it is, please let us know via a Comment
more

Connor and Chris don't just spend all day on AskTOM. You can also catch regular content via Connor's blog and Chris's blog. Or if video is more your thing, check out Connor's channel and Chris's channel from their Youtube channels. And of course, keep up to date with AskTOM via the official twitter account.

More to Explore

SQL

The Oracle documentation contains a complete SQL reference.