How do I solve this delete query error using PHP

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1.00/5 (1 vote)

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<?php
include "connection.php";

$sql = "DELETE FROM add_products_manually WHERE id='" . $_GET["id"] . "'";
if (mysqli_query($link, $sql)) {
    echo "Record deleted successfully";
} else {
    echo "Error deleting record: " . mysqli_error($link);
}
$mysq = "DELETE FROM add_loose-product WHERE id='" . $_GET["id"] . "'";
if (mysqli_query($link, $mysq)) {
    echo "Record deleted successfully";
} else {
    echo "Error deleting record: " . mysqli_error($link);
}

?>

What I have tried:

I have tried to delete the record from the database and it was successfully executed until two records from the database table were deleted and now I'm getting this error as below:-
Record deleted successfully Error deleting record: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '-product WHERE id='7'' at line 1<

Posted 6-Dec-21 0:19am

kalyani yelgaonkar

Updated 6-Dec-21 0:44am

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OriginalGriff · Answer 1 · 2021-12-06T00:44:00

Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

But you also have a problem in your second SQL: "-" is not a valid character in a table name ...