如何检查PHP中的列值是null还是0？

Question

$query = 'select column from table ...';

...


$row = mysql_fetch_assoc($result);

//now i have the result
//but how to check if it's null or 0?

Answer 1

Pandiya的 意思是is_null 。

Answer 2

try

$res=mysql_query(" SELECT NULL AS anullcol, 0 AS anum, '' AS emptystring ");
var_dump(mysql_fetch_assoc($resource));

and read up on the '===' and '!==' operators.

C.

Answer 3

if($var == '' || $var == NULL){
//Code
}

Answer 4

You can use isset():

$foo = 0;
echo isset($foo)  ? 'yes' : 'no';
echo "<br>";

$foo = null;
echo isset($foo) ? 'yes' : 'no';

will result in

yes
no

Answer 5

Maybe you are asking if the Query has returned anything. So try using:

mysql_num_rows()

from PHP:

Retrieves the number of rows from a result set. This command is only valid for statements like SELECT or SHOW that return an actual result set. To retrieve the number of rows affected by a INSERT, UPDATE, REPLACE or DELETE query, use mysql_affected_rows().

<?php
if ( mysql_num_rows ( $query ) == 0){
echo "duh, nothing!";
}
?>

Answer 6

maybe replace the null with an identifier in the select:

select coalesce(column, -1) as column 
from table ...

that way you can test for 0 or -1 (NULL).