diff --git a/notes/pics/next-key-locks.png b/notes/pics/next-key-locks.png
new file mode 100644
index 00000000..94cf0dee
Binary files /dev/null and b/notes/pics/next-key-locks.png differ
diff --git a/notes/数据库系统原理.md b/notes/数据库系统原理.md
index ec7b72c6..59006f30 100644
--- a/notes/数据库系统原理.md
+++ b/notes/数据库系统原理.md
@@ -362,6 +362,8 @@ SELECT c FROM t WHERE c BETWEEN 10 and 20 FOR UPDATE;
 (20, +∞)
 ```
 
+<div align="center"> <img src="pics/next-key-locks.png" width="560px"/> </div><br>
+
 ## 七、关系数据库设计理论
 
 ### 函数依赖