You don't understand how the replacements are meant to be used. The $$ replacements are not ?. I know that. They are for cases where you want a general piece of SQL that will always be the same, a big set of joins or a complex where, but other parts like limit or the feilds might change. In those cases ? would do you no good. Here on the other hand you can now use the $$ to substitute in actual SQL. $$ would always be done by the actual code, unlike ? that would normaly be user supplied (and untainted) data.