I've run into ODBC drivers that did not cope very well with placeholders and executing statements multiple times, substr() doesn't fix everything when you do sometimes want wildcards at the beginning of a string, and if I might have wildly varying numbers of "?" in "IN (?,?,?)" type clauses, I usually just go with quote().
in reply to Re^5: Variable interpolation in a file to be read in
in thread Variable interpolation in a file to be read in