diff --git a/scripts/m11b2c_a3_patch_tx_write.py b/scripts/m11b2c_a3_patch_tx_write.py
index 7ac5aa8..71537b3 100644
--- a/scripts/m11b2c_a3_patch_tx_write.py
+++ b/scripts/m11b2c_a3_patch_tx_write.py
@@ -53,13 +53,14 @@ def _has_db_default(fd):
     写路径按语义不填它们；若计入必填集合，合法调用会被误报缺列。
     （与 _recognize nullable 写法配套：只修识别不修默认值排除，事件表主链路会被误挡。）
     """
+    if "default" not in fd:
+        return False
     dv = fd.get("default")
     if dv is None:
         return False
-    s = str(dv).strip()
-    if s == "" or s.upper() in ("NULL", "NONE"):
+    if str(dv).strip().upper() in ("NULL", "NONE"):
         return False
-    return True
+    return True   # 含 DEFAULT ''（空串默认值同样是 DDL 默认值，数据库会补值）
 
 
 def required_columns(table):