Question

How to combine these two sql queries into one?

SELECT DISTINCT * FROM rss WHERE MATCH(content,title) AGAINST ('$filter') 

SELECT COUNT(content) FROM rss WHERE MATCH(content,title) AGAINST ('$filters')

And if the result is 0 from the above query

–

SELECT DISTINCT * FROM rss WHERE content LIKE '%$filters%' OR title LIKE '%$filters%'; 
$filter .= $row['filter'];
$filters = $row['filter'];

$filters may be more than one keyword

Answer 1

You do not have to use query 2,

mysql_num_rows will indicate how many rows for query 1, so just discard query 2

if mysql_num_rows return zero, then proceed with query 3

To combine three queries into one, use OR

SELECT DISTINCT * FROM rss 
WHERE 
  (MATCH(content,title) AGAINST ('$filter'))
OR
  (content LIKE '%$filter%' OR title LIKE '%$filter%')

As explained above, you do not really need to do count first.

If $filter contains lots of keyword, then just repeating like

  (content LIKE '%$filter_1%' OR title LIKE '%$filter_1%') OR
  (content LIKE '%$filter_2%' OR title LIKE '%$filter_2%') OR ...