故障排除 PHP MySQL 查询

Question

I am trying to run this query:

$q1 = "INSERT INTO `Validation` (`Key`, `Status`, `Notes`, `Serial`) VALUES (max(Key)+1, 'Valid', '".mysql_real_escape_string($user)."', '0')";

through my PHP script, but each time it displays this error:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'Key)+1, 'Valid', 'USER', '0')' at line 1

Any ideas?

Answer 1

KEY is a MySQL reserved word , so if you've picked it as a column name, you must quote it (with backticks) every time:

$q1 = "INSERT INTO `Validation` (`Key`, `Status`, `Notes`, `Serial`) 
    VALUES (
        max(`Key`) + 1, 
        'Valid', 
        '".mysql_real_escape_string($user)."'
        , '0'
    )";

Note that you don't have to quote non-reserved words with backticks.

I'm not actually sure that this will work -- doesn't MySQL prohibit reading from the same table that you're updating in a single query still? Regardless, as mentioned in the comments, it looks like you're just replicating by hand what AUTO_INCREMENT does for you automatically. Consider using it instead.

Answer 2

I'm not sure you can use Key there. One way round this would be to do a SELECT statement before the INSERT to find out the max(Key) value. Another (preferable) way would be to make the database auto increment the KEY column

Answer 3

Try using a subquery.

$q1 = "INSERT INTO `Validation` (`Key`, `Status`, `Notes`, `Serial`) VALUES ((SELECT max(Key) FROM Validation)+1, 'Valid', '".mysql_real_escape_string($user)."', '0')";