Preparing a MySQL INSERT/UPDATE statement with DEFAULT values

Question

Quoting MySQL INSERT manual - same goes for UPDATE:

Use the keyword DEFAULT to set a column explicitly to its default value. This makes it easier to w

Answer 1

Try changing this:

$statement = $pdoObject->
    prepare("INSERT INTO table1 (column1,column2) values (?,?)");
$statement->execute(array('value1','DEFAULT'));

To this:

$statement = $pdoObject->
    prepare("INSERT INTO table1 (column1,column2) values (?,DEFAULT)");
$statement->execute(array('value1'));

It seems to me that your original code will give you this:

INSERT INTO table1 (column1,column2) values ('value1','DEFAULT')

My code should give you this:

INSERT INTO table1 (column1,column2) values ('value1',DEFAULT)

Answer 2

I tried replying to VolkerK answer, but couldnt find how. :( I'm kinda new to all this.

Anyway, I created a mysql function to use in conjuction with his COALESCE idea

CREATE FUNCTION NULLDEFAULT(colname VARCHAR(64), tablename VARCHAR(64), dbname VARCHAR(64)) RETURNS longtext DETERMINISTIC READS SQL DATA
BEGIN
    DECLARE retval longtext;
    SELECT
        COLUMN_DEFAULT INTO retval 
    FROM
        information_schema.COLUMNS
    WHERE
        TABLE_NAME = tablename
    AND
        COLUMN_NAME = colname
    AND
        TABLE_SCHEMA = dbname;

    RETURN retval;
END

You would use it like this:

$stmt = $pdo->prepare("
  INSERT INTO
    foo
    (x,y,z)
  VALUES
    (
      Coalesce(:x, NULLDEFAULT('x', 'foo', 'database')),
      Coalesce(:y, NULLDEFAULT('y', 'foo', 'database')),
      Coalesce(:z, NULLDEFAULT('z', 'foo', 'database'))
    )
");

That will return null if the column has no default value, and won't trigger the "Column has no default value" Error.

Of course you could modify it to not require the database parameter

Answer 3

i think that it is writing the String 'DEFAULT ' because it is escaped by pdo so there are parametres for bindvalue where you can specify the type of the value given so you can send a null with no quotes and it will be PDO::PARAM_NULL; and then default values will be put , but i'm not sure if there are similar parameters when binding with execute

  if(is_int($param)){$pdoParam = PDO::PARAM_INT;}
      elseif(is_bool($param)){$pdoParam = PDO::PARAM_BOOL;}
      elseif(is_null($param)){ $pdoParam = PDO::PARAM_NULL;}
      elseif(is_string($param)){$pdoParam = PDO::PARAM_STR;}
                                    else{$pdoParam = FALSE;}
              $this->_query->bindValue($k,$param,$pdoParam);

Answer 4

The only "workaround" I know for this is to use Coalesce() and Default(fieldname)

E.g.

$pdo = new PDO("mysql:host=localhost;dbname=test", 'localonly', 'localonly'); 
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$pdo->exec("
  CREATE TEMPORARY TABLE foo (
    id int auto_increment,
    x int NOT NULL DEFAULT 99,
    y DATETIME NOT NULL DEFAULT '2010-03-17 01:00:00',
    z varchar(64) NOT NULL DEFAULT 'abc',
    primary key(id)
  )
");


$stmt = $pdo->prepare('
  INSERT INTO
    foo
    (x,y,z)
  VALUES
    (
      Coalesce(:x, Default(x)),
      Coalesce(:y, Default(y)),
      Coalesce(:z, Default(z))
    )
');
$stmt->bindParam(':x', $x);
$stmt->bindParam(':y', $y);
$stmt->bindParam(':z', $z);


$testdata = array(
  array(null, null, null),
  array(1, null, 'lalala'),
  array(null, '2009-12-24 18:00:00', null)
);
foreach($testdata as $row) {
  list($x,$y,$z) = $row;
  $stmt->execute();
}
unset($stmt);
foreach( $pdo->query('SELECT id,x,y,z FROM foo', PDO::FETCH_NUM) as $row) {
  echo join(', ', $row), "\n";
}

prints

1, 99, 2010-03-17 01:00:00, abc
2, 1, 2010-03-17 01:00:00, lalala
3, 99, 2009-12-24 18:00:00, abc