SQL SELECT query echoing twice even with DISTINCT - php

Question

I am creating a simple SQL query in PHP - and for some reason, even when DISTINCT is used, it shows twice like this:
BC
BC
OH
OH
TX
TX
Here is my code:
<?php
$sql = "SELECT DISTINCT `title`,`extra_fields_search` FROM `blahblah_items` WHERE catid=336 ORDER BY `blahblah_items`.`extra_fields_search` ASC ";
$partnerlisting= mysql_query($sql) or die(mysql_error());
while($row = mysql_fetch_assoc($partnerlisting))
foreach($row as $cname => $cvalue){
echo '<li>'.substr($row[extra_fields_search], 0, 2).'</li><br>';
}
;
?>
How can I make it so it prints out only one of each?

Answer 1

SELECT
`title`,
`extra_fields_search`
FROM
`blahblah_items`
WHERE
catid=336
GROUP BY
SUBSTRING(extra_fields_search,1,2) # here. group by first two characters of extra_fields_search
# or just "GROUP BY extra_fields_search", depends what you need
ORDER BY
`blahblah_items`.`extra_fields_search` ASC
SELECT DISTINCT a,b FROM table works in same way as SELECT a,b FROM table GROUP BY a,b
Please follow documentation:
http://dev.mysql.com/doc/refman/5.0/en/distinct-optimization.html
http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html

Answer 2

Distinct make sure that you get unique rows. It does not make sure you will get unique column values. In your case if you consider all the fields in the result, you will notice that each row is different from the other by at least one field.
SO you will never get
Col1 Col2
A B
A B
But you can get
Col1 Col2
A B
A C

Answer 3

Try:
SELECT `title`, group_concat(distinct `extra_fields_search`)
FROM `blahblah_items`
WHERE catid=336
Group BY `title`
ORDER BY 2

Answer 4

try this
SELECT `title`,`extra_fields_search`
FROM `blahblah_items` WHERE catid=336
Group BY extra_fields_search
ORDER BY `blahblah_items`.`extra_fields_search` ASC
edit :
try this in your code
while($row = mysql_fetch_assoc($partnerlisting))
$rows[] = $row;
foreach($rows as $row){
echo '<li>'.substr($row[extra_fields_search], 0, 2).'</li><br>';
}
;