MySQL差異同步是一種用于同步數據庫中數據的工具，它可以在數據庫中的多個實例之間自動同步數據。其原理是通過在主數據庫上進行數據更改，并通過二進制日志中的記錄將更改反映到從數據庫中。

在主數據庫上啟用二進制日志功能，并在從數據庫上使用MySQL Replication Slave I/O Thread和MySQL Replication Slave SQL Thread兩個線程進行差異同步。
mysql>show variables like 'log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_bin       | ON    |
+---------------+-------+
mysql>call mysql.rds_start_replication;
+------------------+-------------+-------------+
| Replica_Server_ID | Master_Host | Master_Port |
+------------------+-------------+-------------+
|              3002 | 172.16.0.12 |        3306 |
+------------------+-------------+-------------+

在主數據庫上更改數據后，mysql會將更改保存到二進制日志中，之后從數據庫上的兩個線程會將更改信息同步到從數據庫中：

mysql>insert into user values('user1','123456');
Query OK, 1 row affected (0.01 sec)
mysql>select * from user;
+---------+--------+
| user    | pwd    |
+---------+--------+
| user1   | 123456 |
+---------+--------+
mysql>show binlog events in 'mysql-bin.000001';
+---------------+-----+----------------+-----------+-------------+------------+
| Log_name      | Pos | Event_type     | Server_id | End_log_pos | Info       |
+---------------+-----+----------------+-----------+-------------+------------+
| mysql-bin.000001 |   4 | Format_desc    |         1 |         120 | MySQL replication: xid 7 |
| mysql-bin.000001 | 120 | Query          |         1 |         180 | insert into user values('user1','123456') |
| mysql-bin.000001 | 180 | Xid            |         1 |         211 | MySQL_commit_ts: 964 |
+---------------+-----+----------------+-----------+-------------+------------+
mysql>select * from user limit 1;
+---------+--------+
| user    | pwd    |
+---------+--------+
| user1   | 123456 |
+---------+--------+

以上是MySQL差異同步的簡單介紹，希望對你有所幫助。