MySQL与PHP的基础与应用专题之数据完整性

<?php

# 创建连接
$conn = mysqli_connect("localhost", "root", "admin", "study");

# 查看是否连接成功
if ($conn) {
    echo "服务器连接成功!";
} else {
    echo mysqli_connect_error();
}

# SQL语句 (身份证带唯一性)
$SQL = "CREATE TABLE user_with_id (
    id INT(8) AUTO_INCREMENT PRIMARY KEY comment '主键id',
    username VARCHAR(255) NOT NULL comment '姓名',
    id_number varchar(255) UNIQUE NOT NULL comment '身份证号'
)";

# 执行SQL语句
$result = mysqli_query($conn, $SQL);

# 查看是否执行成功
if ($result) {
    echo "SQL语句执行成功!";
} else {
    echo mysqli_error($conn);
}

# 关闭连接
mysqli_close($conn);

?>

<?php

# 创建连接
$conn = mysqli_connect("localhost", "root", "admin", "study");

# 查看是否连接成功
if ($conn) {
    echo "服务器连接成功!";
} else {
    echo mysqli_connect_error();
}

# SQL语句, 创建学生表
$SQL1 = "CREATE TABLE student (
    student_id INT(8) PRIMARY KEY COMMENT '学生id',
    student_name VARCHAR(255) NOT NULL COMMENT '学生姓名'
)";

# SQL语句, 创建成绩表
$SQL2 = "CREATE TABLE grade (
    id INT(8) AUTO_INCREMENT PRIMARY KEY COMMENT '主键id',
    student_id INT(8) NOT NULL COMMENT '学生id',
    course varchar(255) NOT NULL COMMENT '课程',
    grade INT(8) NOT NULL COMMENT '成绩',
    FOREIGN KEY (student_id) references student(student_id)
)";

# 执行SQL语句
$result = mysqli_query($conn, $SQL1);

# 查看是否执行成功
if ($result) {
    echo "SQL语句执行成功!";
} else {
    echo mysqli_error($conn);
}

# 执行SQL语句
$result = mysqli_query($conn, $SQL2);

# 查看是否执行成功
if ($result) {
    echo "SQL语句执行成功!";
} else {
    echo mysqli_error($conn);
}

# 关闭连接
mysqli_close($conn);

?>

<?php

# 创建连接
$conn = mysqli_connect("localhost", "root", "admin", "study");

# 查看是否连接成功
if ($conn) {
    echo "服务器连接成功!";
} else {
    echo mysqli_connect_error();
}

# SQL语句, 向主表添加数据
$SQL1 = "INSERT INTO student
    (student_id, student_name)
    VALUES(1, '我是小白呀'),
    (2, '我是大白呀')";

# 执行SQL语句
$result = mysqli_query($conn, $SQL1);

# SQL语句, 向从表添加数据
$SQL2 = "INSERT INTO grade
    (student_id, course, grade)
    VALUES(1, '语文', 59),
    (2, '语文', 99)";

# 执行SQL语句
$result = mysqli_query($conn, $SQL2);

# 查看是否执行成功
if ($result) {
    echo "SQL语句执行成功!";
} else {
    echo mysqli_error($conn);
}

# 关闭连接
mysqli_close($conn);

?>

<?php

# 创建连接
$conn = mysqli_connect("localhost", "root", "admin", "study");

# 查看是否连接成功
if ($conn) {
    echo "服务器连接成功!";
} else {
    echo mysqli_connect_error();
}

# SQL语句, 错误展示 (主表没有student_id=3)
$SQL = "INSERT INTO grade
    (student_id, course, grade)
    VALUES(3, '语文', 88)";

# 执行SQL语句
$result = mysqli_query($conn, $SQL);

# 查看是否执行成功
if ($result) {
    echo "SQL语句执行成功!";
} else {
    echo mysqli_error($conn);
}

# 关闭连接
mysqli_close($conn);

?>