Mysql query built my phpmyadmin doesn't work in PHP with WHERE clauses

Question

Just trying to select all rows with no comments, or comments < 5 characters.

Starting from basics, this works:

$query= "SELECT * FROM `comments`";
$result = mysql_query($query);

What doesn't work is:

$query = "SELECT * FROM `comments` WHERE `comment` = ''";

or

$sql = "SELECT * from comments WHERE LENGTH(comment) < 5 LIMIT 30";

I've put limit 5 because when I do a COUNT on the "empty" comments, it says there's 4 bytes there. The column is not NULL (don't blame me, I didn't write it!)

I've even tried using phpmyadmin to change the "empty" values to the word "chicken", then running

So, I used phpmyadmin to change all the instances of comments < 4 characters to the word "chicken".

$query = "SELECT * FROM `comments` WHERE `comment` = 'chicken'";

As with ALL of the above errors, it spews out:

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 '' at line 1

But if I do

$emptycomment = "chicken";
$query = sprintf("SELECT * FROM `comments` WHERE `comment` = $emptycomment");

Invalid query: Unknown column 'chicken' in 'where clause'

WTF?! But that works perfectly in phpmyadmin! (all above tested on stable and alpha versions)

I also saw where someone else put:

$query = sprintf("SELECT * FROM `comments` WHERE `comment` = 'chicken'");

Again, no dice on any of the above.

The stupid thing is, these all work perfectly directly as a mysql query, and the above were even generated by phpmyadmin! I've even updated php to 5.3.2, the mysql installed is 5.1.52

I've tried making it EXACTLY as per example 2 here, using variables for everything. http://php.net/manual/en/function.mysql-query.php

I've followed the tutorial here: http://www.devshed.com/c/a/MySQL/Null-and-Empty-Strings/3/

I've browsed about 20 articles here at Stackoverflow.

It's 11:15am. I started at 6:30. Getting a bit frustrated here. Thanks!

Answer 1

$emptycomment = "chicken"; $query = sprintf("SELECT * FROM comments WHERE comment = $emptycomment");

Have you tried to print $query after? You missed quotes around string variable

$query = "SELECT * FROM comments WHERE comment = '" . mysql_real_escape_string($comment) . "'";

Answer 2

I ran into a similar problem where an "empty" field wasn't NULL. What happens if you try the chicken with:

$query = "SELECT * FROM comments WHERE comment LIKE '%chicken%'";

This will give you a match even if you have CR/LF and other strange "invisible" characters involved.

Answer 3

From my experience the query generated by phpmyadmin puts quotes where I believe there shouldn't be any such as table names and once I remove those it works. IE "SELECT * FROM 'db'.'table'" doesn't work but "SELECT * FROM table" does.