How to check if MySQL returns null/empty?

Question

In DB I have a table with a field called fk_ownerID. By default, when I add a new table row, the fk_ownerID is empty. In Toad for MySQL, this is shown as {null}. If fk_ownerID is given a value, and I later remove this value, I set fk_ownerID = "".

Now, I have the following code:

$result = $dal->getRowByValue('tableName','id', $_POST['myID']);

// Check to see if any rows where returned
if (mysql_num_rows($result) > 0)
{
  while ($row = mysql_fetch_array($result))
  {
    $ownerID = $row["fk_ownerID"];    
  }
}

Now the variable $ownerID should have a number, or not. But I'm unsure how to check this. Currently I'm doing this:

if ( (strlen($ownerID) == 0) || ($ownerID == '0') || ($ownerID == 'null') )

But I'm pretty sure only one of these tests should be necessary.

What is the best way to check if a row field is empty or null?

scragar · Accepted Answer · 2009-11-07 15:57:54Z

50

Use empty() and/or is_null()

http://www.php.net/empty http://www.php.net/is_null

Empty alone will achieve your current usage, is_null would just make more control possible if you wanted to distinguish between a field that is null and a field that is empty.

edited Nov 7, 2009 at 15:57

answered Nov 7, 2009 at 15:38

scragar

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3 Comments

Steven Over a year ago

So I have to use empty() AND is_null()?

Steven Over a year ago

ok.... empty() should do :) --> Returns FALSE if var has a non-empty and non-zero value. The following things are considered to be empty: "" (an empty string) 0 (0 as an integer) "0" (0 as a string) NULL FALSE array() (an empty array) var $var; (a variable declared, but without a value in a class)

Mateng Over a year ago

I reckon that is_null() is safer, because if a variable has a zero value it's still considered empty().

Community · Accepted Answer · 2020-06-20 09:12:55Z

10

You can use is_null() function.

http://php.net/manual/en/function.is-null.php : in the comments :

mdufour at gmail dot com 20-Aug-2008 04:31 Testing for a NULL field/column returned by a mySQL query.

Say you want to check if field/column “foo” from a given row of the table “bar” when > returned by a mySQL query is null. You just use the “is_null()” function:

[connect…]
$qResult=mysql_query("Select foo from bar;");
while ($qValues=mysql_fetch_assoc($qResult))
     if (is_null($qValues["foo"]))
         echo "No foo data!";
     else
         echo "Foo data=".$qValues["foo"];
[…]

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Nov 7, 2009 at 15:38

Valentin Golev

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Comments

Sunil Kumar · Accepted Answer · 2015-02-16 12:31:05Z

3

select FOUND_ROWS();

will return no. of records selected by select query.

answered Feb 16, 2015 at 12:31

Sunil Kumar

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Comments

Citizen · Accepted Answer · 2009-11-07 17:08:31Z

1

Also, don't forget the === operator when you're working with numbers that could mean null or 0 or return some form of false or null that isn't what you're looking for.

answered Nov 7, 2009 at 17:08

Citizen

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2 Comments

AStopher Over a year ago

This doesn't answer the question.

Citizen Over a year ago

I agree, should have been left as a comment.

user8588978 · Accepted Answer · 2020-01-07 06:00:48Z

1

if ( (strlen($ownerID) == 0) || ($ownerID == '0') || (empty($ownerID )) )

if $ownerID is NULL it will be triggered by the empty() test

https://www.php.net/empty

answered Jan 7, 2020 at 6:00

user8588978

Comments

Spinstaz · Accepted Answer · 2021-10-26 09:50:25Z

0

If your datatype in your mysql database is an auto-increment primary key, then you can't use is_null() you must use empty() or in code, it would be if (empty($id)) {

answered Oct 26, 2021 at 9:50

Spinstaz

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Comments

Omkar Frozen · Accepted Answer · 2015-02-20 05:10:03Z

-6

Suppose

$row=mysql_fetch_row($rc)
and if you want to check if row[8] is null then do
$field=$row[8];
   if($field)
echo "";
else
 echo "";

answered Feb 20, 2015 at 5:10

Omkar Frozen

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