def gene():
nonlocal context
assert len(self._fields)
if self._where:
context.varWhereExpr = str(self._where)
for field, expr in self._fields:
c = Context(namespace=Names.Update.ColumnsLevel)
c.varColumnName = field.Name
c.varColumnUpdateExpr = expr
context.level(c)
return self.builder.build(context)
