PHP develops simple book backend system to create database and tables

First create a database about books, named book.

<?php
// 创建连接
$conn = new mysqli("localhost", "uesename", "password");
// 检测连接
if ($conn->connect_error) 
{    
    die("连接失败: " . $conn->connect_error);} 
    // 创建数据库
    $sql = "CREATE DATABASE book";
        if ($conn->query($sql) === TRUE) 
        {    
        echo "数据库创建成功";
        } else {    
        echo "Error creating database: " . $conn->error;
        }
    $conn->close();
?>

Create an administrator table in the database, named admin

Set the following fields:

id: It is unique, of type int, and selects the primary key.

username: Administrator name, type is varchar, length is 50.

password: Password, type is varchar, length is 50.

<?php
$SQL = " CREATE TABLE IF NOT EXISTS `admin` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(50) CHARACTER SET utf8 DEFAULT NULL,
  `password` varchar(50) CHARACTER SET utf8 DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=2 ";
?>

Here we need to continue to use the yx_book table of "PHP to develop a simple book lending system"

The fields are as follows:

id: It is unique, type is int, and Select the primary key.

name: Book name, type is varchar, length is 20.

price: Price, type decimal(4,2), used for data storage with relatively high precision.

The declaration syntax of decimal column is decimal(m,d).

1. M is the maximum number of numbers (precision). Its range is 1 to 65 (in older MySQL versions, the allowed range was 1 to 254).
        2. D is the number of digits to the right of the decimal point (scale). Its range is 0~30, but it must not exceed M.

uploadtime: storage time, type is datetime.

type: Book classification, type is varchar, length is 10.

total: Number of books, type is int, length is 50.

leave_number: The number of remaining books that can be borrowed, type is int, length is 10.

<?php
$SQL = " CREATE TABLE IF NOT EXISTS `yx_books` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) CHARACTER SET utf8 NOT NULL,
  `price` decimal(4,2) NOT NULL,
  `uploadtime` datetime NOT NULL,
  `type` varchar(10) CHARACTER SET utf8 NOT NULL,
  `total` int(50) DEFAULT NULL,
  `leave_number` int(10) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=42 ";
?>

Write the created database table into the config.php file so that we can call the database table on different pages in the future.

<?php
ob_start();
session_start(); //开启缓存
header("Content-type:text/html;charset=utf-8");
$link = mysqli_connect('localhost','username','password','book');
mysqli_set_charset($link, "utf8");
if (!$link) {
  die("连接失败:".mysqli_connect_error());
}
?>