Why would Mysql's Round(N.DD,1) sometimes show no digits after the decimal place when using the Perl DBI?
This was unrelated to MySQL and was due to a change in the Perl DBD::mysql packages from version 4.013 to 4.042. Essentially, DBD::mysql now attempts to coerce the MySQL datatype into a Perl datatype. So, previously, a float of 4.0 would be returned as a string '4.0', but now the same float will be returned as a numeric value and be displayed as '4' when printed (without additional formatting on the part of Perl.