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!

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Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 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.

Method 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';

Method 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;

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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