插入数据库MAX（field）+1

Question

I am trying to insert some values into a database, one of the values that I need to insert is;- MAX(FixedFareID)+1

As follows:

public function fixed($fieldDay) {

    $pdo = new SQL();
    $dbh = $pdo->connect(Database::$serverIP, Database::$serverPort, Database::$dbName, Database::$user, Database::$pass);

    $this->sql = "INSERT INTO tblfixedfare VALUES (NULL, MAX(FixedFareID)+1, '1', '$fieldDay')";

Obviously, as it is this will not work, but I am unsure how I could insert the MAX(FixedFareID)+1 value into the database.

Any help would be much appreciated.

Answer 1

INSERT INTO tblfixedfare 
select NULL, MAX(FixedFareID)+1, '1', '$fieldDay' from tblfixedfare 

Answer 2

最好的方法是使用auto_increment列（语法取决于您的SQL引擎）或使用序列。

Answer 3

Use a sub query:

$this->sql = 
  "INSERT INTO tblfixedfare 
  VALUES (NULL, (SELECT MAX(FixedFareID)+1 FROM tblfixedfare), '1', '$fieldDay'";

Answer 4

You are doing it wrong. You need a sub-select for your MAX() :

(SELECT MAX(FixedFareID)+1 FROM tblfixedfare)

or, which may be a better and faster, switch your FixedFareID to use auto increment feature.

Answer 5

If you do not have an auto increment field then you can use something like this:

INSERT INTO tblfixedfare 
SELECT NULL, MAX(FixedFareID)+1, '1', '$fieldDay'
FROM tblfixedfare

So your code would be:

public function fixed($fieldDay) {

    $pdo = new SQL();
    $dbh = $pdo->connect(Database::$serverIP, Database::$serverPort, Database::$dbName, Database::$user, Database::$pass);

    $this->sql = "INSERT INTO tblfixedfare SELECT NULL, MAX(FixedFareID)+1, '1', '$fieldDay' FROM tblfixedfare";