When the comparison string ('ABC%' and 'ABC') is fixed.  

AH ok

Well, the result is not always the same: I just found out that you should be careful when working with :variables, for example in %SQLQuery:

select 1 where 'well...' %startswith :myvar

Returns 1 row for myvar being null.

Whereas

select 1 where 'well...' like :myvar||'%';

Does return no row for myvar being null.

Using IRIS for Windows (x86-64) 2021.1 (Build 215) Wed Jun 9 2021 09:56:33 EDT

Great tip, Marc! Thanks for your help