11. mysqli 学习

内容参考 mysqli的官网，和w3c英文版

1. mysqli 连接

<?php
$servername = "localhost";
$username = "username";
$password = "password";

// Create connection
$conn = new mysqli($servername, $username, $password);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 
echo "Connected successfully";
?>

1.a

mysqli:

面向对象风格

mysqli::__construct ([ string $host = ini_get("mysqli.default_host") [, string $username = ini_get("mysqli.default_user") [, string $passwd = ini_get("mysqli.default_pw") [, string $dbname = "" [, int $port = ini_get("mysqli.default_port") [, string $socket = ini_get("mysqli.default_socket") ]]]]]] )

l host：连接的服务器地址。

l username：连接数据库的用户名，默认值是服务器进程所有者的用户名。

l passwd：连接数据库的密码，默认值为空。

l dbname：连接的数据库名称。

l port：TCP端口号。

l socket：UNIX域socket。

2 create database

<?php
$servername = "localhost";
$username = "username";
$password = "password";

// Create connection
$conn = new mysqli($servername, $username, $password);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

// Create database
$sql = "CREATE DATABASE myDB";
if ($conn->query($sql) === TRUE) {
    echo "Database created successfully";
} else {
    echo "Error creating database: " . $conn->error;
}

$conn->close();
?>

3. create table

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

// sql to create table
$sql = "CREATE TABLE MyGuests (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY, 
firstname VARCHAR(30) NOT NULL,
lastname VARCHAR(30) NOT NULL,
email VARCHAR(50),
reg_date TIMESTAMP
)";

if ($conn->query($sql) === TRUE) {
    echo "Table MyGuests created successfully";
} else {
    echo "Error creating table: " . $conn->error;
}

$conn->close();
?>

NOT NULL - Each row must contain a value for that column, null values are not allowed
DEFAULT value - Set a default value that is added when no other value is passed
UNSIGNED - Used for number types, limits the stored data to positive numbers and zero
AUTO INCREMENT - MySQL automatically increases the value of the field by 1 each time a new record is added
PRIMARY KEY - Used to uniquely identify the rows in a table. The column with PRIMARY KEY setting is often an ID number, and is often used with AUTO_INCREMENT

4. insert data

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$sql = "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('John', 'Doe', 'john@example.com')";

if ($conn->query($sql) === TRUE) {
    echo "New record created successfully";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();
?>

5. prepared statements

可以把一些常用的表达式存起来省的每次都query那么多

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// prepare and bind
$stmt = $conn->prepare("INSERT INTO MyGuests (firstname, lastname, email) VALUES (?, ?, ?)");
$stmt->bind_param("sss", $firstname, $lastname, $email);

// set parameters and execute
$firstname = "John";
$lastname = "Doe";
$email = "john@example.com";
$stmt->execute();

$firstname = "Mary";
$lastname = "Moe";
$email = "mary@example.com";
$stmt->execute();

$firstname = "Julie";
$lastname = "Dooley";
$email = "julie@example.com";
$stmt->execute();

echo "New records created successfully";

$stmt->close();
$conn->close();
?>

5.a

bind_param :

$stmt = $mysqli->prepare("INSERT INTO CountryLanguage VALUES (?, ?, ?, ?)");
$stmt->bind_param('sssd', $code, $language, $official, $percent);

其中：

i corresponding variable has type integer
d corresponding variable has type double
s corresponding variable has type string
b corresponding variable is a blob and will be sent in packets

6. select data

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
    }
} else {
    echo "0 results";
}
$conn->close();
?>

6.a

where：

example ：$sql = "SELECT * FROM MyGuests WHERE id = 2";

SELECT column FROM table
WHERE column operator value

运算符说明
= 等于
!= 不等于
> 大于
< 小于
>= 大于或等于
<= 小于或等于
BETWEEN 介于一个包含范围内
LIKE 搜索匹配的模式

6.b

ordered by

SELECT column_name(s)
FROM table_name
ORDER BY column_name

如果降序：

SELECT column_name(s)
FROM table_name
ORDER BY column_name DESC

如果多列（第一列相同，比第二列）：

SELECT column_name(s)
FROM table_name
ORDER BY column_name1, column_name2

6.c

update:

UPDATE table_name
SET column_name = new_value
WHERE column_name = some_value

6.d

delete：

DELETE FROM table_name
WHERE column_name = some_value

11. mysqli 学习

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