add

doc/faq/backend/db_isolation_levels.md

@@ -59,6 +59,7 @@ Consistent reads within the same transaction read the snapshot established by th
 
 - https://blog.amis.com/database-transaction-isolation-a1e448a7736e
 - https://www.mysql.tw/2023/05/mysql-lock.html
+- https://fanyilun.me/2015/12/29/%E4%BA%8B%E5%8A%A1%E7%9A%84%E9%9A%94%E7%A6%BB%E7%BA%A7%E5%88%AB%E4%BB%A5%E5%8F%8AMysql%E4%BA%8B%E5%8A%A1%E7%9A%84%E4%BD%BF%E7%94%A8/
 - https://blog.csdn.net/weixin_45670060/article/details/119977481
 - https://ithelp.ithome.com.tw/articles/10194749
 - https://myapollo.com.tw/blog/database-transaction-isolation-levels/

doc/faq/backend/lock.md

@@ -81,8 +81,33 @@ unlock tables
 
 
 #### 行級鎖
+	- InnoDB 引擎是支援行級鎖定的，而 MyISAM 引擎並不支援行級鎖定
+
+```sql
+# sql
+
+# SQL client 1
+# 对读取的记录加共享锁
+# select * from accounts where id = 5 lock in share mode;
+select * from authors where id = 1 lock in share modes;
+
+
+# 对读取的记录加独占锁
+select * from authors for update;
+
+# SQL client 2
+```
 
 
 ### 2) Redis Lock
 
-### 3) Zookeeper (ZK) Lock
+### 3) Zookeeper (ZK) Lock
+
+### 4) Modern DB deal with concurrence:
+
+- Types
+ - 2PL (2 phase locking)
+ - MVCC (Multiversion concurrency control) (多版本並行控制)
+
+- Ref
+ - https://www.fanyilun.me/2017/04/20/MySQL%E5%8A%A0%E9%94%81%E5%88%86%E6%9E%90/?source=post_page-----19833c18baab--------------------------------