Incorrect parameter when using IsNull in MySQL

I've been trying to use the IsNull() function to ensure that there is a value for a field.

SELECT crawled.id,
       IsNull(sranking.score,0) as Score,
       crawled.url,
       crawled.title,
       crawled.blurb
FROM crawled
    LEFT JOIN sranking ON crawled.id = sranking.sid
WHERE crawled.body LIKE '%".$term."%'
ORDER BY Score DESC LIMIT " . $start . "," . $c

But I get the error message:

Incorrect parameter count in the call to native function 'IsNull'

Anybody have any ideas? 开发者_C百科I'm pretty new to MySQL.

ISNULL tests if the passed expression is NULL. What you need is IFNULL, or COALESCE, as xyld has mentioned.

SELECT crawled.id, IFNULL(sranking.score, 0) as Score, ...

You might consider using coalesce: http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#function_coalesce

It returns the first non-null value.