从数据库 mySQL PHP 生成自动事务 ID

Question

I am trying to generate the transaction number while I am inserting the data in my database through PHP. I want to generate the sequence transaction id, so that I am doing the below SQL. I am counting the ID column and add +1 value for new inserts. but when I have a bulk insert it will not for after a single entry and showing different transaction id.

I want the ALFABHETs will always constant and after the number will continuously run. if the number will be reached then, it will automatically become 3 to 4 digits.

For example, the number will start from MG001 . If MG999 then it will becomes to MG1000 , MG1001 , MG1002 etc

#table_name: table1

ID | transactionID  
------------------
1  | MG001
2  | MG001
3  | MG003
4  | MG004
5  | MG004
6  | MG001

$stmt = $con->prepare("SELECT * FROM `table1` ORDER BY `ID` DESC LIMIT 1");
$stmt->execute();
if ($stmt->rowCount() > 0) {
    while ($data = $stmt->fetch()) {
        $transactionCode = 'MG' . $data['ID'] + 1;
    }
} else {
    $transactionCode = 'MG001' . '1';
}

Answer 1

Your query loads the record with the highest ID, which is a single record and adds 1 to it if found. If there was no record, then you use 'MG0011' as value. Since you have a single value, if you put that into your bulk insert's code, then it will be duplicated. So you should load transactionID (and not ID), strip the MG or whatever prefix from it and add 1 to it. Example:

$stmt = $con->prepare("SELECT * FROM `table1` ORDER BY `ID` DESC LIMIT 1");
$stmt->execute();
if ($stmt->rowCount() > 0) {
    while ($data = $stmt->fetch()) {
        $transactionCode = (int)substr($data['transactionID'], 2) + 1;
    }
} else {
    $transactionCode = 1;
}

The code above generates a starting point and does not care (yet) about the format that you intend to use. Now, let's implement a function that generates the code as you need it:

function generateTransactionCode($input, $prefix = 'MG') {
    while (strlen($input) < 3) $input = '0'.$input;
    return $prefix.$input;
}

And now let's generate a bulk insert command (I assume that you auto_increment the ID ):

$sql = 'insert into table1(transactionID) values';
$values = [];
for ($index = 0; $index < 5; $index++) { //we insert 5 values in this example
    $values[]='('.generateTransactionCode($transactionCode + $index).')';
}
$sql .= implode(',', $values);
//Execute the insert

It's more tricky to do that with insert select statements. If you need to do that, then you will need to use row_number .