SQL - IF EXISTS UPDATE ELSE INSERT INTO

What I'm trying to do is INSERT subscribers in my database, but IF EXISTS it should UPDATE the row, ELSE INSERT INTO a new row.

Ofcourse I connect to the database first and GET the $name, $email and $birthday from the url string.

$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'];

This works, but just adds the new row;

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

Here's what I tried;

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);

and

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);

and

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);

But none of them work, what am I doing wrong?

Any help is greatly appreciated!

1. Create a UNIQUE constraint on your subs_email column, if one does not already exist:

    ALTER TABLE subs ADD UNIQUE (subs_email)
   

2. Use 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

3. Note that I have used parameter placeholders in the place of string literals, as one really should be using parameterised statements to defend against SQL injection attacks.

Try this:

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

INSERT ... ON DUPLICATE KEY UPDATE

is a good solution as long as you don't mind AUTO_INCREMENT counters unnecessarily incrementing every time you end up doing an UPDATE. Since it tries to INSERT first, I noticed auto counters do increment. Another solution I like that may be less performant, but easy to maintain is:

IF EXISTS(SELECT 1 FROM table WHERE column = value...) THEN
	UPDATE table 
    SET column = value ...
    WHERE other_column = other_value ...;
ELSE
	INSERT INTO table
		(column1, column2, ...)
	VALUES
		(value1, value2, ...);
END IF;