mysql - SQL - 如果存在更新 ELSE INSERT INTO

Question

我要做的是 INSERT 我的数据库中的订阅者，但是 IF EXISTS 它应该 UPDATE 行， ELSE INSERT INTO 一个新行。

当然，我首先连接到数据库，然后 GET $name、$email 和 $birthday 来自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'];

这可行，但只是添加新行；

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，我做错了什么？

非常感谢任何帮助!

Answer 1

1. 创建 UNIQUE constraint在您的 subs_email 列中，如果尚不存在:

   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)
   

You can use the VALUES(col_name) function in the UPDATE clause to refer to column values from the INSERT portion of the INSERT ... ON DUPLICATE KEY UPDATE - dev.mysql.com

1. 请注意，我使用参数占位符代替字符串文字，因为一个 真的 应该使用参数化语句来 defend against SQL injection attacks .