MySQL force query to return NULL

Question

I have the following:

SELECT q25, COUNT( q25 ) AS count, AVG (q1) AS q1
FROM tresults WHERE id = 'Yes' AND date = 'MARCH2010' AND q25 = '1' 
GROUP BY q25

At the moment, the query returns MySQL returned an empty result set (i.e. zero rows). which is correct - is it possible to get it to return NULL instead?

OR

Is there a way of dealing with this after the event in PHP, such as:

$resultprev = mysql_query($queryprev);
if($resultprev == ''){
// do something
}

That sounds like a phpMyAdmin message. Where do you need the null exactly? — JJJ
– JJJ, Commented Feb 24, 2012 at 9:56
I need this otherwise other code doesn't run correctly. I need the null under 'q1'. Alternatively, can this be dealt with after, see the edit above. Thanks. — Homer_J
– Homer_J, Commented Feb 24, 2012 at 9:58

Manse · Accepted Answer · 2012-02-24 10:03:58Z

3

use mysql_num_rows :

$resultprev = mysql_query($queryprev);
$num_rows = mysql_num_rows($resultprev);
if($num_rows == 0){
   // 0 results !
}

or you could union a null row :

SELECT q25, COUNT( q25 ) AS count, AVG (q1) AS q1
FROM tresults WHERE id = 'Yes' AND date = 'MARCH2010' AND q25 = '1' 
GROUP BY q25

UNION

SELECT null, null as count, null as q1

edited Feb 24, 2012 at 10:03

answered Feb 24, 2012 at 9:57

Manse

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1 Comment

JJJ Over a year ago

Answers the literal question, but seems rather convoluted for what the OP actually needs.

silly · Accepted Answer · 2012-02-24 10:04:55Z

2

try this

if(mysql_affected_rows($res)) {
    //your stuff
}

or in sql

SELECT (
    SELECT q25, COUNT( q25 ) AS count, AVG (q1) AS q1
    FROM tresults WHERE id = 'Yes' AND date = 'MARCH2010' AND q25 = '1' 
    GROUP BY q25

    UNION

    SELECT null, null, null

) AS x
LIMIT 1

edited Feb 24, 2012 at 10:04

answered Feb 24, 2012 at 9:59

silly

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