SQL - 如果存在更新ELSE INSERT INTO

Question

我想要做的是INSERT我的数据库中的用户，但IF EXISTS它应该UPDATE行，ELSE INSERT INTO一个新的行。

当然我首先连接到数据库，GET$name,$email和$birthday从url字符串。

$con=mysqli_connect("localhost","---","---","---"); 
// Check connection 
if (mysqli_connect_errno()) 
    { 
    echo "Failed to connect to MySQL: " . mysqli_connect_error(); 
    } 

$name=$_GET['name']; 
$email=$_GET['email']; 
$birthday=$_GET['birthday']; 

这个工作，但只是增加了新的行;

mysqli_query($con,"INSERT INTO subs (subs_name, subs_email, subs_birthday) 
VALUES ('$name', '$email', '$birthday')"); 

mysqli_close($con); 

这是我试过的;

mysqli_query($con,"INSERT INTO subs (subs_name, subs_email, subs_birthday) 
VALUES '$name', '$email', '$birthday' 
ON DUPLICATE KEY UPDATE subs_name = VALUES($name), subs_birthday = VALUES($birthday)"); 
mysqli_close($con); 

和

mysqli_query($con,"IF EXISTS (SELECT * FROM subs WHERE subs_email='$email') 
    UPDATE subs SET subs_name='$name', subs_birthday='$birthday' WHERE subs_email='$email' 
ELSE 
    INSERT INTO subs (subs_name, subs_email, subs_birthday) VALUES ('$name', '$email', '$birthday')"); 
mysqli_close($con); 

和

mysqli_query($con,"IF NOT EXISTS(SELECT * FROM subs WHERE subs_email='$email') 
Begin 
INSERT INTO subs (subs_name, subs_email, subs_birthday) 
VALUES ('$name', '$email', '$birthday') 
End"); 
mysqli_close($con); 

但他们没有工作，我究竟做错了什么？

任何帮助，非常感谢！

Answer 1

1. 您subs_email列创建UNIQUE constraint，如果一个尚不存在：

   ALTER TABLE subs ADD UNIQUE (subs_email) 
   

2. 使用INSERT ... ON DUPLICATE KEY UPDATE：

   INSERT INTO subs 
       (subs_name, subs_email, subs_birthday) 
   VALUES 
       (?, ?, ?) 
   ON DUPLICATE KEY UPDATE 
       subs_name  = VALUES(subs_name), 
       subs_birthday = VALUES(subs_birthday) 
   

您可以使用VALUES （col_name）函数中UPDATE子句 指列值从插入的插入部... ON DUPLICATE密钥更新 - dev.mysql.com

注意，我在地方使用参数占位符字符串文字，作为一个真的应该使用参数化语句defend against SQL injection attacks。