diff --git a/README.md b/README.md
index b0bbae1..4d6f766 100644
--- a/README.md
+++ b/README.md
@@ -167,6 +167,7 @@ Base on Spring-Boot
             </p>
             <ol>
                 <li><p><del>Fix CVE-2019-3778, use spring-security-oauth 2.3.5.RELEASE</del></p></li>             
+                <li><p><del>解决数据库多条 access_token问题，增加唯一约束</del></p></li>             
             </ol>
             <br/>
        </li>  
diff --git a/others/database/oauth.ddl b/others/database/oauth.ddl
index 3c75667..397a0e2 100644
--- a/others/database/oauth.ddl
+++ b/others/database/oauth.ddl
@@ -26,7 +26,7 @@ create table oauth_access_token (
   create_time timestamp default now(),
   token_id VARCHAR(255),
   token BLOB,
-  authentication_id VARCHAR(255),
+  authentication_id VARCHAR(255) UNIQUE,
   user_name VARCHAR(255),
   client_id VARCHAR(255),
   authentication BLOB,