diff --git a/user-defined-variables.md b/user-defined-variables.md
index f81304eecaaa6..53bc0392476dd 100644
--- a/user-defined-variables.md
+++ b/user-defined-variables.md
@@ -178,4 +178,8 @@ SELECT @col FROM t;
 +------+
 ```
 
+## MySQL compatibility
+
+Except for `SELECT ... INTO <variable>`, the syntax supported in MySQL and TiDB is identical.
+
 For more information, see [User-Defined Variables in MySQL](https://dev.mysql.com/doc/refman/5.7/en/user-variables.html).