How to query the database in php

How to query the database in php: 1. Use the function [mysql_connect()] to establish a connection with the MYSQL database; 2. Use the function [mysql_select_db()] to specify the database to be operated; 3. Use the function [mysql_query( )】Query command.

【Related learning recommendations: Database learning】

php query database method:

1. Function method

mysql_connect(): Used to create There are 5 parameters in total when connecting to the MYSQL database. Normally, only the first 3 parameters are used. The three parameters are the MySQL server address, username and password.

mysql_select_db(): Used to specify the database to be operated. If the database to be operated has not been created, you must first create the database and then create the tables in the database.

mysql_query(): A dedicated function for query instructions. All SQL statements are executed through it and the result set is returned.

mysql_fetch_row(): Get a row from the result set as enumeration data, get a row of data from the result set associated with the specified result identifier and return it as an array.

mysql_fetch_array(): Gets a row from the result set as an associative array, a numeric array, or both. In addition to storing the data in the array as a numeric index, it also Data can be stored as a relational index, using field names as keys.

mysql_fetch_object(): Get a row from the result set as an object, and use the field name as an attribute.

mysql_fetch_assoc(): Get a row from the result set as an associative array, which means that this function cannot use the index to get the value like mysql_fetch_row, but can only use the field name to get the value.

mysql_num_rows(): Get the number of rows in the result set queried by the select statement

2. Example

<?php
    /* 连接数据库服务器，用or die的目的为了即使连接错误，系统不会继续执行，而是返回错误*/
    $link=mysql_connect("localhost","root","12345678") or die("数据库连接失败");
      /* 连接数据库*/
      mysql_select_db("phptest",$link);
      /*设置字符集，使得页面的编码与数据库的编码一致。如果不一致将出现中文乱码*/
      mysql_query("set names utf8");
      /*定义数据库命令查询*/
      $q="select*from tb_user";
      /*执行数据库查询*/
      $result=mysql_query($q);
      /*执行数据库记录*/
      while($row=mysql_fetch_assoc($result)){
          echo "<tr><td>".$row["id"]."</td><td>".$row["username"]."</td><td>".$row["password"]."</td></tr>";
             /*显示数据结果*/
      }
?>

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