mf = en.getField(head.name());
String colName = head.name();
if (mf != null)
colName = mf.getColumnName();
sql.append(colName).append("=");
if (head.special()) {
if (head.value() != null && head.value() instanceof String) {
String str = (String)head.value();
if (str.length() > 0) {
switch (str.charAt(0)) {
case '+':