--- a/about.php
+++ b/about.php
@@ -32,7 +32,7 @@
 <?php
 include_once("./lib/common.inc.php");
 $query = 'SELECT DATE("importDate") as importday, count(*) as count, min("publishDate") as start, max("publishDate") as end 
-FROM contractnotice WHERE "childCN" = 0 AND "parentCN" = 0 AND DATE("importDate") = (select * from (SELECT DATE("importDate") 
+FROM contractnotice WHERE "childCN" is null AND "parentCN" is null AND DATE("importDate") = (select * from (SELECT DATE("importDate") 
 FROM contractnotice ORDER BY "importDate" DESC limit 1) alias) GROUP BY DATE("importDate")';
 $query = $conn->prepare($query);
 	$query->execute();
@@ -45,7 +45,7 @@
 
 
 $query = 'SELECT DATE("importDate") as importday, count(*) as count, min("publishDate") as start, max("publishDate") as end 
-FROM contractnotice WHERE ("childCN" != 0 OR "parentCN" != 0) AND DATE("importDate") = (select * from (SELECT DATE("importDate") 
+FROM contractnotice WHERE ("childCN" is not null OR "parentCN" is not null) AND DATE("importDate") = (select * from (SELECT DATE("importDate") 
 FROM contractnotice ORDER BY "importDate" DESC limit 1) alias) GROUP BY DATE("importDate")';
 $query = $conn->prepare($query);
 	$query->execute();