Are you looking for this little tidbit buried in the DBI POD?

       Constants representing the values of the SQL standard types can
+ be
       imported individually by name, or all together by importing the
+ special
       ":sql_types" tag.

       The names and values of all the defined SQL standard types can 
+be pro-
       duced like this:

         foreach (@{ $DBI::EXPORT_TAGS{sql_types} }) {
           printf "%s=%d\n", $_, &{"DBI::$_"};
         }
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