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php warning mysql_fetch_assoc

I have a weird problem about my script. It returns always error for mysql_fetch_array or mysql_fetch_assoc. I have used mysql_fetch many times in my project and I checked for this error many times but I am blind about what is happening. Is there something wrong about my script?

My functions aim is learning the biggest value of specified mysql field.

Here is the function:

function nextIncrement($table,$field) {
    $sql = mysql_query("SELECT '$field' FROM '$table' ORDER BY '$field' DESC LIMIT 0,1");
    while($row = mysql_fetch_assoc($sql)) {
        $next = $row[$field];
    }
    $next = (int)$next;
    return $next;
}

Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource ...

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  • Seems like your SQL query is failing. Commented Dec 13, 2010 at 10:55

3 Answers 3

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Most likely, your mysql_query() returned false for some reason.

See the manual for a list of possible values that mysql_query() can return.

Do a echo mysql_error(); to see what's wrong.

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7 Comments

Query works fine in sql editor but it returns error when I echo: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 'ORDER BY 'fbUserReceipeId' DESC LIMIT 0,1' at line 1')' at line 1
@Ahmet try backticks in the table name: ` instead of '
Oh Pekka thank you very much. It worked. But what is the difference? And what is it's shortcut :)
@Ahmet backticks are used to quote table names
Weird thing is I used ' instead of backtick many times with no problem. Thank you. What is shortcut for backtick
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Check to see that the query actually succeeds before proceeding to fetch results.

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3 Comments

Yeah it succeeds. It returns one row and one column as I wish. Everythinh seems OK, right?
How do you determine that it succeeds? Your function will return something in every case, the return will be 0 if there is no result or an error within the query.
I tested it writing table's and field's name directly. It was work everytime with ' but this time didn't. Pekka's solution which is using backticks worked. Thanks @Ignacio and @Dr.Molle for suggestions.
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There may be an error in your SQL statement, or maybe you don't have an open database connection?

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