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.

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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, ...

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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.