这篇文章将为大家详细讲解有关Mysql数据库数据更新失效的原因和解决方法，小编觉得挺实用的，因此分享给大家做个参考，希望大家阅读完这篇文章后可以有所收获。
1. 背景
最近的项目中遇到一项问题，并发更新某一单据的时候，出现了更新失效的情况。比如：
@Transactional(rollbackFor = Exception.class)
public void update(Integer id){
//1.按id查询
//2.更新某一字段的值
}生成的SQL大概是这样的：
UPDATE table
SET field = #{field,jdbcType=INTEGER}
WHERE id= 1那么以上代码产生的问题就是：
对于同一个id=1来说，请求A与请求B都进到了update方法中，此时按id查询得到的信息是相同的，那么请求A更新了id=1的这条记录之后，此时，请求B又对id=1的记录进行更新，此时注意请求B更新id=1的记录的时候，请求B按id查询到的数据已经是旧数据了，请求B执行完之后，请求A的更新被请求B覆盖了。
如果更新的是状态，那倒无所谓，如果库存量呢？
如果更新的是库存，是在这条记录的原始值上进行+或者-操作，是不是就出问题了？
2. 分析产生的原因
事后写了个小demo来复现问题，代码大致如下：
需求： 某个分类每被访问一次，排序就+1；
开启两个客户端同时访问
@Transactional(rollbackFor = Exception.class)
public void updateStatusTest(Integer id) {
System.out.println("start:"+Thread.currentThread().getName());
Category category = categoryMapper.selectById(id);
try {
Thread.sleep(8000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+":"+category);
category.setSort(category.getSort()+1);
categoryMapper.updateById(category);
category = categoryMapper.selectById(id);
System.out.println(Thread.currentThread().getName()+":"+category);
System.out.println("end:"+Thread.currentThread().getName());
}DAO层使用的mybatis，生成日志大致如下：
需要更新的sort值数据库初始为：0
start:http-nio-8062-exec-1
Creating a new SqlSession
Registering transaction synchronization for SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6df7e3e9]
JDBC Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@2d5c951c] will be managed by Spring
==> Preparing: SELECT cid,category_name,parent_id,image_url,icon_url,sort,status FROM t_admin_category WHERE cid=?
==> Parameters: 6(Integer)
<== Columns: cid, category_name, parent_id, image_url, icon_url, sort, status
<== Row: 6, 1, 0, 11111, 1, 0, 1111
<== Total: 1
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6df7e3e9]
Time：27 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.selectById
Execute SQL：
SELECT
cid,
category_name,
parent_id,
image_url,
icon_url,
sort,
status
FROM
t_admin_category
WHERE
cid=6
start:http-nio-8062-exec-2
Creating a new SqlSession
Registering transaction synchronization for SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7af43046]
JDBC Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@700c5b36] will be managed by Spring
==> Preparing: SELECT cid,category_name,parent_id,image_url,icon_url,sort,status FROM t_admin_category WHERE cid=?
Time：2 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.selectById
Execute SQL：
SELECT
cid,
category_name,
parent_id,
image_url,
icon_url,
sort,
status
FROM
t_admin_category
WHERE
cid=6
==> Parameters: 6(Integer)
<== Columns: cid, category_name, parent_id, image_url, icon_url, sort, status
<== Row: 6, 1, 0, 11111, 1, 0, 1111
<== Total: 1
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7af43046]
http-nio-8062-exec-1:Category{cid=6, categoryName='1', parentId=0, imageUrl='11111', iconUrl='1', sort=0, status='1111'}
Fetched SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6df7e3e9] from current transaction
==> Preparing: UPDATE t_admin_category SET category_name=?, parent_id=?, image_url=?, icon_url=?, sort=?, status=? WHERE cid=?
==> Parameters: 1(String), 0(Integer), 11111(String), 1(String), 1(Integer), 1111(String), 6(Integer)
Time：16 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.updateById
Execute SQL：
UPDATE
t_admin_category
SET
category_name='1',
parent_id=0,
image_url='11111',
icon_url='1',
sort=1,
status='1111'
WHERE
<== Updates: 1
cid=6
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6df7e3e9]
Time：0 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.selectById
Execute SQL：
Fetched SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6df7e3e9] from current transaction
SELECT
cid,
category_name,
==> Preparing: SELECT cid,category_name,parent_id,image_url,icon_url,sort,status FROM t_admin_category WHERE cid=?
parent_id,
==> Parameters: 6(Integer)
image_url,
icon_url,
<== Columns: cid, category_name, parent_id, image_url, icon_url, sort, status
sort,
status
<== Row: 6, 1, 0, 11111, 1, 1, 1111
FROM
<== Total: 1
t_admin_category
WHERE
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6df7e3e9]
cid=6
http-nio-8062-exec-1:Category{cid=6, categoryName='1', parentId=0, imageUrl='11111', iconUrl='1', sort=1, status='1111'}
end:http-nio-8062-exec-1
Transaction synchronization committing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6df7e3e9]
Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6df7e3e9]
Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6df7e3e9]
http-nio-8062-exec-2:Category{cid=6, categoryName='1', parentId=0, imageUrl='11111', iconUrl='1', sort=0, status='1111'}
Fetched SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7af43046] from current transaction
==> Preparing: UPDATE t_admin_category SET category_name=?, parent_id=?, image_url=?, icon_url=?, sort=?, status=? WHERE cid=?
Time：0 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.updateById
Execute SQL：
UPDATE
t_admin_category
SET
category_name='1',
parent_id=0,
image_url='11111',
icon_url='1',
sort=1,
status='1111'
WHERE
cid=6
==> Parameters: 1(String), 0(Integer), 11111(String), 1(String), 1(Integer), 1111(String), 6(Integer)
<== Updates: 1
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7af43046]
Fetched SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7af43046] from current transaction
==> Preparing: SELECT cid,category_name,parent_id,image_url,icon_url,sort,status FROM t_admin_category WHERE cid=?
==> Parameters: 6(Integer)
<== Columns: cid, category_name, parent_id, image_url, icon_url, sort, status
<== Row: 6, 1, 0, 11111, 1, 0, 1111
Time：16 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.selectById
Execute SQL：
SELECT
cid,
category_name,
<== Total: 1
parent_id,
image_url,
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7af43046]
icon_url,
sort,
status
FROM
http-nio-8062-exec-2:Category{cid=6, categoryName='1', parentId=0, imageUrl='11111', iconUrl='1', sort=0, status='1111'}
t_admin_category
end:http-nio-8062-exec-2
WHERE
cid=6大致意思：
请求A与请求B，同时操作id=6的这条记录时，查询出来id=6的这条记录，然后请求A对其进行了修改 SET sort=1操作，完事之后，请求A的事务提交了。而此时请求B，通过id=6条件查询到的category的信息是请求A提交之前的，此时请求B执行了SET sort=1，覆盖了请求B的修改操作。
3. 解决思路
解决方法其它很简单，我们上面可以看到，update语句是直接set sort=1的，我们只需要改为set sort = sort +1 就可以了。你不信？那我改一下试试：
@Transactional(rollbackFor = Exception.class)
public void updateStatusTest(Integer id) {
System.out.println("start:"+Thread.currentThread().getName());
Category category = categoryMapper.selectById(id);
try {
Thread.sleep(8000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+":"+category);
// category.setSort(category.getSort()+1);
categoryMapper.updateStatusById(category);
category = categoryMapper.selectById(id);
System.out.println(Thread.currentThread().getName()+":"+category);
System.out.println("end:"+Thread.currentThread().getName());
}Mapper文件：
<update id="updateStatusById" parameterType="com.sxl.simple.shop.admin.category.entity.Category">
UPDATE
t_admin_category
SET
sort =sort + 1
WHERE
cid= #{cid,jdbcType=INTEGER}
</update>我们执行试一下，看下日志：
start:http-nio-8062-exec-1
Creating a new SqlSession
Registering transaction synchronization for SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e925f3f]
JDBC Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@6c17839b] will be managed by Spring
==> Preparing: SELECT cid,category_name,parent_id,image_url,icon_url,sort,status FROM t_admin_category WHERE cid=?
==> Parameters: 6(Integer)
<== Columns: cid, category_name, parent_id, image_url, icon_url, sort, status
<== Row: 6, 1, 0, 11111, 1, 0, 1111
<== Total: 1
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e925f3f]
Time：43 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.selectById
Execute SQL：
SELECT
cid,
category_name,
parent_id,
image_url,
icon_url,
sort,
status
FROM
t_admin_category
WHERE
cid=6
start:http-nio-8062-exec-2
Creating a new SqlSession
Registering transaction synchronization for SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6c88f022]
JDBC Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@195f8b5a] will be managed by Spring
==> Preparing: SELECT cid,category_name,parent_id,image_url,icon_url,sort,status FROM t_admin_category WHERE cid=?
==> Parameters: 6(Integer)
<== Columns: cid, category_name, parent_id, image_url, icon_url, sort, status
<== Row: 6, 1, 0, 11111, 1, 0, 1111
<== Total: 1
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6c88f022]
Time：2 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.selectById
Execute SQL：
SELECT
cid,
category_name,
parent_id,
image_url,
icon_url,
sort,
status
FROM
t_admin_category
WHERE
cid=6
http-nio-8062-exec-1:Category{cid=6, categoryName='1', parentId=0, imageUrl='11111', iconUrl='1', sort=0, status='1111'}
Fetched SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e925f3f] from current transaction
==> Preparing: UPDATE t_admin_category SET sort =sort + 1 WHERE cid= ?
==> Parameters: 6(Integer)
<== Updates: 1
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e925f3f]
Fetched SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e925f3f] from current transaction
==> Preparing: SELECT cid,category_name,parent_id,image_url,icon_url,sort,status FROM t_admin_category WHERE cid=?
Time：0 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.updateStatusById
Execute SQL：
UPDATE
t_admin_category
SET
sort =sort + 1
WHERE
cid= 6
==> Parameters: 6(Integer)
Time：0 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.selectById
<== Columns: cid, category_name, parent_id, image_url, icon_url, sort, status
Execute SQL：
<== Row: 6, 1, 0, 11111, 1, 1, 1111
SELECT
<== Total: 1
cid,
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e925f3f]
category_name,
parent_id,
http-nio-8062-exec-1:Category{cid=6, categoryName='1', parentId=0, imageUrl='11111', iconUrl='1', sort=1, status='1111'}
image_url,
end:http-nio-8062-exec-1
icon_url,
sort,
Transaction synchronization committing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e925f3f]
status
FROM
Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e925f3f]
t_admin_category
WHERE
Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5e925f3f]
cid=6
Time：0 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.updateStatusById
Execute SQL：
UPDATE
t_admin_category
SET
sort =sort + 1
WHERE
cid= 6
Time：0 ms - ID：com.sxl.simple.shop.admin.category.mapper.CategoryMapper.selectById
Execute SQL：
SELECT
cid,
category_name,
parent_id,
image_url,
icon_url,
sort,
status
FROM
t_admin_category
WHERE
cid=6
http-nio-8062-exec-2:Category{cid=6, categoryName='1', parentId=0, imageUrl='11111', iconUrl='1', sort=0, status='1111'}
Fetched SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6c88f022] from current transaction
==> Preparing: UPDATE t_admin_category SET sort =sort + 1 WHERE cid= ?
==> Parameters: 6(Integer)
<== Updates: 1
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6c88f022]
Fetched SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6c88f022] from current transaction
==> Preparing: SELECT cid,category_name,parent_id,image_url,icon_url,sort,status FROM t_admin_category WHERE cid=?
==> Parameters: 6(Integer)
<== Columns: cid, category_name, parent_id, image_url, icon_url, sort, status
<== Row: 6, 1, 0, 11111, 1, 2, 1111
<== Total: 1
Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6c88f022]
http-nio-8062-exec-2:Category{cid=6, categoryName='1', parentId=0, imageUrl='11111', iconUrl='1', sort=2, status='1111'}
end:http-nio-8062-exec-2看完上述内容，你们对Mysql数据库数据更新失效的原因和解决方法大概了解了吗？如果想了解更多相关文章内容，欢迎关注亿速云行业资讯频道，感谢各位的阅读！
