弄清楚如何用php和mysql做到这一点

问题描述：

I have a variety of fields. id | lat1 | lon1 | lat2 | lon2 |

I need a way to check if data on lat1 is null, and if is null then put data in it. I was trying this:

$selec2 = "SELECT lat1 FROM usuarios WHERE androidid='$Id'";
$checklat = mysql_query($selec2, $link);

if (is_resource($checklat) and mysql_num_rows($checklat) = 0){
        $row = mysql_fetch_array($checklat);
}
else if (is_null($row)){ 
        $queif5 = mysql_query($updatelat, $link) or die(mysql_error());
        }

Thanks in advance.

我有各种各样的字段。 id | lat1 | lon1 | lat2 | lon2 | p>

我需要一种方法来检查lat1上的数据是否为空，如果为null则将数据放入其中。我试图这样做： p>

  $ selec2 =“SELECT lat1 FROM usuarios WHERE androidid ='$ Id'”; 
 $ checklat = mysql_query（$ selec2，$ link）; 
 
if（is_resource（$ checklat）和mysql_num_rows（  $ checklat）= 0）{
 $ row = mysql_fetch_array（$ checklat）; 
} 
else if（is_null（$ row））{
 $ queif5 = mysql_query（$ updatelat，$ link）or die（mysql_error（  ））; 
} 
  code>  pre> 
 
 提前致谢。 p> 
  div>

答

You could try it in MYSQL using IFNULL like:

SELECT IFNULL(lat1, 'default') FROM usuarios WHERE androidid='$Id'

A side note, you should be using prepared statement to avoid SQL vulnerability.

弄清楚如何用php和mysql做到这一点

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