SQL - IF EXISTS UPDATE ELSE INSERT INTO - mysql

Question

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!

Answer 1

Create a UNIQUE constraint on your subs_email column, if one does not already exist:
ALTER TABLE subs ADD UNIQUE (subs_email)
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
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.

Answer 2

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';

Answer 3

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;