SQL-如果存在，则将更新插入其他

我想要做的就是INSERT在我的数据库的用户，但IF EXISTS它应该UPDATE排，ELSE INSERT INTO一个新行。

Ofcourse我连接到数据库第一和GET的$name，$email并$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'];

可以，但是只添加新行；

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

mysqli_close($con);

这是我尝试过的；

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);

但是它们都不起作用，我在做什么错呢？

任何帮助是极大的赞赏！

1. 如果不存在UNIQUE约束，请在您的subs_email列上创建约束：

   ALTER TABLE subs ADD UNIQUE (subs_email)
   

2. 用途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)
   

您可以在UPDATE子句中使用VALUES（col_name）函数来引用INSERT的INSERT部分中的列值。... ON DUPLICATE KEY UPDATE-dev.mysql.com

3. 请注意，我已经使用参数占位符代替字符串文字，因为实际上应该使用参数化语句来防御SQL注入攻击。

试试这个：

INSERT INTO `center_course_fee` (`fk_course_id`,`fk_center_code`,`course_fee`) VALUES ('69', '4920153', '6000') ON DUPLICATE KEY UPDATE `course_fee` = '6000';