diff --git a/xls2ddl/tmpls.py b/xls2ddl/tmpls.py
index 0b9f615..65e0e65 100644
--- a/xls2ddl/tmpls.py
+++ b/xls2ddl/tmpls.py
@@ -329,9 +329,12 @@ return {
 """
 data_update_tmpl = """
 ns = params_kw.copy()
-for k,v in ns.items():
-	if v == 'NaN' or v == 'null':
-		ns[k] = None
+for k,v in list(ns.items()):
+	if v == 'NaN' or v == 'null' or v == '' or v is None:
+		if k != 'id':
+			del ns[k]
+		else:
+			ns[k] = None if v in ('NaN', 'null') else v
 {% if logined_userid %}
 userid = await get_user()
 if not userid:
@@ -374,6 +377,9 @@ for _fname, _rules in _validation_rules.items():
 \t_val = params_kw.get(_fname, '')
 \tif _val is None: _val = ''
 \t_val = str(_val)
+\t# Update: skip validation if field is empty (not modified)
+\tif not _val or _val.strip() == '':
+\t\tcontinue
 \tfor _rule in _rules:
 \t\t_rt = _rule.get('type', '')
 \t\t_rm = _rule.get('message', _fname)