程式碼詳解MySQL中關於事務的處理

這篇文章主要介紹了詳解MySQL中關於事務的處理,小編覺得挺不錯的，現在分享給大家，也給大家做個參考。一起跟著小編過來看看吧

步驟：

#1.開啟事務 start transaction

當我們開啟一個事務的時候，我們對sql的操作都發生在記憶體中，但是沒有真正的回饋到資料庫磁碟的檔案中！

2.回滾 rollback

#回滾，就是恢復到交易開啟之前的最原始的狀態！

注意：回滾操作會自動的關閉一個事務，如果想再次執行事務，需要重新開啟事務！

3.提交 commit

# 

交易的基本原則

 

普通的執行，之所以是立即執行並生效，因為預設的，MySQL對sql語句的執行是自動提交的！所以，開啟一個事務的本質，就是關閉了先前的自動提交的功能，而是由使用者手動提交（利用commit語句）！

總結交易的步驟：

1，  開啟交易

2，  若執行成功，就提交commit

3，  若有任何一條sql語句執行失敗，則回滾rollback！

 

交易處理最典型的就是藉錢。 下面以張三向李四還1000元為例

先查看資料庫中各自的錢數

##下面是處理還錢交易的程式碼：

<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: 14px; margin: 0px; padding: 0px; line-height: 1.5;">php 

</span><span style="font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);">/**
* MySQL实现事务操作<br/>*/<br/><br/></span><span style="font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);">echo</span> "<meta charset=utf-8>"<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>;<br><br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>// 1 连接数据库<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$link</span> = @<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 128);'>mysql_connect</span>('localhost','root','') or <span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>die</span>('连接数据库失败'<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>);<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 128);'>mysql_select_db</span>('test',<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$link</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>);</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 128);'>mysql_query</span>('set names utf8'<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>);<br><br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>// 2  开启事务<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 128);'>mysql_query</span>("start transaction"<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>);<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>//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: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$flag</span> = <span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>true</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>;<br><br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>// 2.1执行事务中的一组sql语句 <br><br>// 李四的money+1000<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$sql</span> = "update pdo set mone=money+1000 where name='李四'"<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>;<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$res</span> = <span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 128);'>mysql_query</span>(<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$sql</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>);<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>if</span> (!<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$res</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>) {   <br>     </span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>//若sql语句执行失败，把$falg设置为false</span>
    <span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$flag</span> = <span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>false</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>;
}<br><br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>//张三的money-1000<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$sql</span> = "update pdo set money=money-1000 where name='张三'"<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>;<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$res</span> = <span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 128);'>mysql_query</span>(<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$sql</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>);<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>if</span> (!<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$res</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>) {  <br>     </span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>//若sql语句执行失败，把$falg设置为false</span>
    <span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$flag</span> = <span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>false</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>;
}<br><br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>// 2.2 判断事务是否执行成功<br></span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>if</span> (<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(128, 0, 128);'>$flag</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>) {   <br>     </span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>//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: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 128);'>mysql_query</span>('commit'<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>);    </span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>echo</span> "还钱成功！"<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>;
}</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>else</span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>{  <br>     </span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 0);'>// 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: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 128, 128);'>mysql_query</span>('rollback'<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>);    </span><span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5; color: rgb(0, 0, 255);'>echo</span> "还钱失败！"<span style='font-family: 微软雅黑, "Microsoft YaHei"; font-size: 14px; margin: 0px; padding: 0px; line-height: 1.5;'>;
}</span></span>

結果：

下面，我們故意把其中一個欄位寫錯，看看交易是否正常處理，資料庫中的錢數是否有變化！

<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>

結果：

結果是還錢失敗，且資料庫中各自的錢數沒有變化，說明當某一條語句未執行成功時，事物不會提交，而會回滾，把資料恢復到開始事務之前的原始狀態，這也是使用事務的作用，即只有當交易中所有sql語句全部執行成功，交易才會提交，否則會回溯！ #

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