https://github.com/mysqljs/mysql/issues/559

SqlString.escape maps both JavaScript null and undefined to MySQL NULL. This change proposes JavaScript undefined be mapped to MySQL DEFAULT, as per feature request mysqljs/mysql#559 and as discussed in mysqljs/mysql#1568.

Author: Derek

lib/SqlString.js

@@ -31,10 +31,14 @@ SqlString.escapeId = function escapeId(val, forbidQualified) {
 };
 
 SqlString.escape = function escape(val, stringifyObjects, timeZone) {
-  if (val === undefined || val === null) {
+  if (val === null) {
     return 'NULL';
   }
-
+  
+  if (val === undefined) {
+    return 'DEFAULT';
+  }
+  
   switch (typeof val) {
     case 'boolean': return (val) ? 'true' : 'false';
     case 'number': return val+'';