PHP - CSV import with auto-increase ID - php

Question

Sorry if this has been asked before, but I couldnt find anything that would relate to my case here on SE.
I am trying to import a CSV file into my Mysql database table with both the table the CSV having the exact same amount and order of columns, except that the table's column ID is not missing in the CSV file.
What I want to achieve is to import the CSV into the table while generating an ID number that automatically increases with each record. This does not seem possible as the CSV always seem to want to insert its data into the first colum in the table, but in my case I would need it to be the 2nd column.
How do I approach this and is there any reference code I can study? I currently am working off this PDO approach but am having the above mentioned difficulties.
PHP
<?php
$databasehost = "localhost";
$databasename = "test";
$databasetable = "sample";
$databaseusername="test";
$databasepassword = "";
$fieldseparator = ",";
$lineseparator = "\n";
$csvfile = "filename.csv";
if(!file_exists($csvfile)) {
die("File not found. Make sure you specified the correct path.");
}
try {
$pdo = new PDO("mysql:host=$databasehost;dbname=$databasename",
$databaseusername, $databasepassword,
array(
PDO::MYSQL_ATTR_LOCAL_INFILE => true,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
)
);
} catch (PDOException $e) {
die("database connection failed: ".$e->getMessage());
}
$affectedRows = $pdo->exec("
LOAD DATA LOCAL INFILE ".$pdo->quote($csvfile)." INTO TABLE `$databasetable`
FIELDS TERMINATED BY ".$pdo->quote($fieldseparator)."
LINES TERMINATED BY ".$pdo->quote($lineseparator));
echo "Loaded a total of $affectedRows records from this csv file.\n";
?>
Thank you

Answer 1

You can have MySQL set values for certain columns during import. If your id field is set to auto increment, you can set it to null during import and MySQL will then assign incrementing values to it.
LOAD DATA LOCAL INFILE ".$pdo->quote($csvfile)." INTO TABLE `$databasetable`
FIELDS TERMINATED BY ".$pdo->quote($fieldseparator)."
LINES TERMINATED BY ".$pdo->quote($lineseparator))."
SET id=null;
EDIT - In case the ID column is not present in CSV
The col1, col2, col3,... are names of actual columns in the DB table (without id column)
LOAD DATA LOCAL INFILE ".$pdo->quote($csvfile)." INTO TABLE `$databasetable`
FIELDS TERMINATED BY ".$pdo->quote($fieldseparator)."
LINES TERMINATED BY ".$pdo->quote($lineseparator))."
(col1, col2, col3,...)
SET id=null;

Answer 2

The AUTO_INCREMENT attribute can be used to generate a unique identity for new rows. Most version of mysql and engin support this. You need not worry about the ID and can use cron job to insert the needed field and AUTO_INCREMENT will take care of the id itself.
No value was specified for the AUTO_INCREMENT column, so MySQL assigned sequence numbers automatically. You can also explicitly assign 0 to the column to generate sequence numbers, unless the NO_AUTO_VALUE_ON_ZERO SQL mode is enabled. If the column is declared NOT NULL, it is also possible to assign NULL to the column to generate sequence numbers. When you insert any other value into an AUTO_INCREMENT column, the column is set to that value and the sequence is reset so that the next automatically generated value follows sequentially from the largest column value.
You can retrieve the most recent automatically generated AUTO_INCREMENT value with the LAST_INSERT_ID() SQL function or the mysql_insert_id() C API function. These functions are connection-specific, so their return values are not affected by another connection which is also performing inserts.
See example from official link :
[https://dev.mysql.com/doc/refman/5.7/en/example-auto-increment.html]

Answer 3

As you want to recreate the table over and over and want to manipulate the Data from the CSV, try this:
// You have to create the TABLE if not exists
$pdo->exec("TRUNCATE TABLE sample"); // No need to drop the table if columns don't change.
$csvContent = file_get_contents($csvfile); // Raw Data from file
$lines = explode("
", $csvContent); // The standard line separator is an ENTER
// Now you have each line separated
for($i = 0; $i < coount($lines); $i++) {
$col = explode(";", $lines[$i]); // Would be a comma
// Now you have each column separated
$pdo->exec("INSERT INTO sample (id, col1, col2, col3 ... coln) VALUES (NULL, '".$col[0]."', '".$col[1]."', '".$col[2]."' ... '".$col[n]."')");
}
This way you can dig into your Data and, besides setting an AUTO_INCREMENT ID, you can validate what is coming from the CSV and can correct/prevent importation errors.