mysql事务问题演示

MySQL/common.sql

@@ -2,7 +2,14 @@
 show global status like 'Innodb_page_size';
 
 # 查询用户
-select * from mysql.user;
+select *
+from mysql.user;
 
 # 查询表的创建语句
-SHOW CREATE TABLE sku.person;
+show create table sku.person;
+
+# 查询某个表占用的空间
+select concat(round(sum(data_length / 1024 / 1024), 2), 'MB') as size
+from information_schema.tables
+where table_schema = 'fortern_qqnt'
+  and table_name = 'group_msg_table';

MySQL/transaction-error/ddl.sql

@@ -0,0 +1,14 @@
+create schema errors;
+-- 生成演示用的表
+create table errors.customer
+(
+    id       int auto_increment
+        primary key,
+    username varchar(50) not null
+);
+create table errors.customer_back
+(
+    id       int auto_increment
+        primary key,
+    username varchar(50) not null
+);

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;

MySQL/transaction-error/user_b.sql

@@ -0,0 +1,20 @@
+-- example 1
+
+-- ========== 1 =========
+start transaction;
+-- B插入数据
+insert into customer (id, username)
+values (1, 'Fortern'),
+       (2, 'Maxin'),
+       (3, 'MooGeo');
+commit;
+-- ========== 2 =========
+
+
+-- example 2
+-- ========== 1 =========
+start transaction;
+-- B 修改所有人的name
+update customer set username = '哈基米' where true;
+commit;
+-- ========== 2 =========