SQL - IF EXISTS UPDATE ELSE INSERT INTO

问题

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!

回答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.

来源：https://stackoverflow.com/questions/15383852/sql-if-exists-update-else-insert-into

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mysql

sql

insert

exists