Iterator<TableRef> iterator = tables.iterator();
while (iterator.hasNext()) {
TableRef tableRef = iterator.next();
try {
PColumn column = tableRef.getTable().getColumn(colName);
if (theTableRef != null) { throw new AmbiguousColumnException(colName); }
theTableRef = tableRef;
theColumnPosition = column.getPosition();
} catch (ColumnNotFoundException e) {
}