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Mysqli的基本操作-CURD的学习开发总结

PHP自5.5起,已经完全废除mysql扩展,官方推荐使用MySQLI或PDO来代替。这篇文章主要讲mysqli的一些基本操作。使用mysqli有两个风格的写法,对象式或函数式,下面我们只展示函数式的写法风格。

数据库连接

首先肯定需要连接数据库。连接数据前,我们需要准备的一般有数据库的账号、密码、端口号、数据库名。

因为网络原因或其他原因经常会有连接不上数据库的情况,所以,我们需要做连接失败的处理。

<?php// 数据库连接$mysqli = mysqli_connect(   'localhost',   'root',   '',   'test');if (mysqli_connect_errno()) {   throw new Exception('databases connect error:'       .mysqli_connect_error());}// ...一些数据库操作// 关闭数据库资源mysqli_close($mysqli);

设置字符集

设置字符集使用mysqli_set_charset();

字符集目前我们大都使用utf8mb4,因为他支持4个字节长度的字符。他支持一些emoji表情字符。当然如果你不需要支持4字节字符的话可以选择使用utf8,因为他比较剩空间。

mysqli_set_chartset($mysqli, 'utf8mb4');

重新选择数据库

数据库连接后,还可以重新选择数据库。

mysqli_select_db($mysqli, '数据库名');

CURD操作

mysqli_query():对数据库执行一次操作,DDL、DQL 、DML都支持。

mysqli_affected_rows():获取影响记录行数。

新增数据操作

mysqli_query($mysqli,   "INSERT INTO users(username, age, sex)               VALUES('周杰伦', 35, '男'),                      ('谢霆锋', 35, '男')");if (mysqli_affected_rows($mysqli) <= 0) {   throw new Exception('databases insert error:'       . mysqli_error($mysqli));}

修改数据操作

这里面有一个注意点,mysqli_affected_rows返回的值为0的情况。它更新的信息与上次完全一样,这个情况很普遍。比如说在修改的时候,连续点击了多次修改按钮。但并不能说明程序代码有问题。所以,和新增不一样的是,返回0也应该是成功状态。

mysqli_query($mysqli,   "UPDATE users SET age=40 WHERE user_id = 1");if (mysqli_affected_rows($mysqli) < 0) {   throw new Exception('databases update error:'       . mysqli_error($mysqli));}

删除数据操作

注意:修改和删除操作必须加where条件,不然将会修改整个表的数据,后果不堪设想(删库跑路o(╯□╰)o)。

mysqli_query($mysqli,   "Delete FROM users  WHERE user_id = 100");if (mysqli_affected_rows($mysqli) <= 0) {   throw new Exception('databases delete error:'       . mysqli_error($mysqli));}

查询操作

当mysqli_query执行的是一条查询语句时,该函数会返回mysqli_result结果集。

mysqli_fetch_all()从结果集中获取全部数据。该函数第二个参数可以指定返回数据的格式。分别为:

  • MYSQLI_NUM:返回索引数组

  • MYSQLI_ASSOC:返回关联数组

  • MYSQLI_BOTH:既有索引数组也有关联数组

另外需要注意,对结果集的操作结束后,记得销毁结果集资源。

// 数据库连接$mysqli = mysqli_connect(   'localhost',   'root',   '',   'test');if (mysqli_connect_errno()) {   throw new Exception('databases connect error:'       .mysqli_connect_error());}mysqli_set_charset($mysqli, 'utf8mb4');$result = mysqli_query($mysqli,   "SELECT * FROM users");if (mysqli_affected_rows($mysqli) < 0) {   throw new Exception('databases select error:'       . mysqli_error($mysqli));}$users = mysqli_fetch_all($result, MYSQLI_ASSOC);// 销毁结果集资源mysqli_free_result($result);// 关闭数据库资源mysqli_close($mysqli);

以上就是Mysqli基本操作,个人实际学习开发总结,欢迎讨论!

以上就是Mysqli的基本操作-CURD的学习开发总结的详细内容,更多请关注求知技术网其它相关文章!

文章来源:智云一二三科技

文章标题:Mysqli的基本操作-CURD的学习开发总结

文章地址:https://www.zhihuclub.com/1278.shtml

关于作者: 智云科技

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