Detailed code explanation of transaction processing in MySQL

This article mainly introduces the detailed explanation of transaction processing in MySQL. The editor thinks it is quite good, so I will share it with you now and give it as a reference. Let’s follow the editor and take a look

Steps:

1. Start transaction start transaction

When we start a transaction, all our SQL operations occur in memory, but there is no real feedback to the file on the database disk!

2. Rollback rollback

Rollback is to restore to the original state before the transaction was started!

Note: The rollback operation will automatically close a transaction. If you want to execute the transaction again, you need to reopen the transaction!

3. Submit commit

Basic principles of transactions

Ordinary execution is executed immediately and takes effect because by default, MySQL automatically submits the execution of the sql statement. ! Therefore, the essence of opening a transaction is to turn off the previous automatic submission function, and instead submit it manually (using the commit statement) by the user!

Summarize the steps of the transaction:

1, Open the transaction

2, If the execution is successful , submit commit

3, If any SQL statement fails to execute, rollback!

#The most typical transaction processing is borrowing and repaying money. The following is an example of Zhang San returning 1,000 yuan to Li Si

First check the respective amounts of money in the database

The following is the code to handle the repayment transaction:

<span style="font-size: 14px; font-family: 微软雅黑, " microsoft yahei><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>php 

</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>/**
* MySQL实现事务操作<br>*/<br><br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>echo</span> "<meta charset="utf-8">"<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>;<br><br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>// 1 连接数据库<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$link</span> = @<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>mysql_connect</span>('localhost','root','') or <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>die</span>('连接数据库失败'<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>);<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>mysql_select_db</span>('test',<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$link</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>);</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>mysql_query</span>('set names utf8'<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>);<br><br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>// 2  开启事务<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>mysql_query</span>("start transaction"<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>);<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>//设置一个变量，用来判断所有sql语句是否成功<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$flag</span> = <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>true</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>;<br><br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>// 2.1执行事务中的一组sql语句 <br><br>// 李四的money+1000<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$sql</span> = "update pdo set mone=money+1000 where name='李四'"<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>;<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$res</span> = <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>mysql_query</span>(<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$sql</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>);<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>if</span> (!<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$res</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>) {   <br>     </span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>//若sql语句执行失败，把$falg设置为false</span>
    <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$flag</span> = <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>false</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>;
}<br><br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>//张三的money-1000<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$sql</span> = "update pdo set money=money-1000 where name='张三'"<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>;<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$res</span> = <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>mysql_query</span>(<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$sql</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>);<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>if</span> (!<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$res</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>) {  <br>     </span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>//若sql语句执行失败，把$falg设置为false</span>
    <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$flag</span> = <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>false</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>;
}<br><br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>// 2.2 判断事务是否执行成功<br></span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>if</span> (<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>$flag</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>) {   <br>     </span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>//所有sql语句执行成功，把sql语句提交</span>
    <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>mysql_query</span>('commit'<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>);    </span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>echo</span> "还钱成功！"<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>;
}</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>else</span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>{  <br>     </span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>// 如其中一条执行失败，则回滚到事务开启之前的状态</span>
    <span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>mysql_query</span>('rollback'<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>);    </span><span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height: color: rgb>echo</span> "还钱失败！"<span style="font-family: 微软雅黑, " microsoft yahei font-size: margin: padding: line-height:>;
}</span></span>

Result:

############## Has the number changed? ######

<span style="font-size: 14px; font-family: 微软雅黑, " microsoft yahei>// 李四的money+1000<br>$sql = "update pdo set mone=money+1000 where name='李四'";  //把moeny字段错写成mone<br></span>

######Result: #############################The result is that the repayment failed , and the respective amounts of money in the database have not changed, indicating that when a certain statement is not executed successfully, the transaction will not be committed, but will be rolled back to restore the data to the original state before starting the transaction. This is also the role of using transactions, that is ###Only when all SQL statements in the transaction are successfully executed, the transaction will be submitted, otherwise it will be rolled back! #########

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