From 93309eaf2aa6131799c6287108bc5f3757e2f5b7 Mon Sep 17 00:00:00 2001
From: Keke Yi <40977455+yikeke@users.noreply.github.com>
Date: Tue, 23 Jun 2020 22:30:47 +0800
Subject: [PATCH] cherry pick #2993 to release-3.0

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
---
 user-defined-variables.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/user-defined-variables.md b/user-defined-variables.md
index bb675d351173e..77a9dc9d56e0a 100644
--- a/user-defined-variables.md
+++ b/user-defined-variables.md
@@ -7,6 +7,10 @@ aliases: ['/docs/v3.0/reference/sql/language-structure/user-defined-variables/',
 
 # User-Defined Variables
 
+> **Warning:**
+>
+> User-defined variables are still an experimental feature. It is **NOT** recommended that you use them in the production environment.
+
 The format of the user-defined variables is `@var_name`. `@var_name` consists of alphanumeric characters, `_`, and `$`. The user-defined variables are case-insensitive.
 
 The user-defined variables are session specific, which means a user variable defined by one client cannot be seen or used by other clients.