mysql事务问题演示

MySQL/transaction-error/user_a.sql

@@ -0,0 +1,42 @@
+-- example 1
+
+-- ========== 0 =========
+start transaction;
+-- A先查询
+select *
+from customer;
+-- ========== 1 =========
+
+-- ========== 2 =========
+-- 在 B 添加数据后，A 尝试进行修改。奇怪的是，明明查询不到，居然可以修改成功
+update customer
+set username = 'wuhu'
+where id = 1;
+-- A 再次查询表中数据，发现修改的那一行现身了
+select *
+from customer;
+commit;
+-- ========== 3 =========
+
+
+-- example 2
+-- ========== 0 =========
+start transaction;
+-- A先查询，查到数据如下：
+-- 1,Fortern
+-- 2,Maxin
+-- 3,MooGeo
+select *
+from customer;
+-- ========== 1 =========
+
+-- ========== 2 =========
+-- A 备份表中数据到另一个表
+insert into customer_back select * from customer;
+commit;
+-- 结果备份表中的数据居然是被其他事物修改的数据！！
+select * from customer_back;
+-- 为什么会这样？
+-- ========== 3 =========
+
+select * from customer where id = 1;