sqlFn = function(v) {
                        return sql.op.replace('?', function() {
                            return v;
                        });
                    }
Returns rules as a SQL query
@param {boolean|string} [stmt] - use prepared statements: false, 'question_mark', 'numbered', 'numbered(@)', 'named', 'named(@)'
@param {boolean} [nl=false] output with new lines
@param {object} [data] - current rules by default
@returns {module:plugins.SqlSupport.SqlQuery}
@fires module:plugins.SqlSupport.changer:getSQLField
@fires module:plugins.SqlSupport.changer:ruleToSQL
@fires module:plugins.SqlSupport.changer:groupToSQL
@throws UndefinedSQLConditionError, UndefinedSQLOperatorError