diff --git a/src/Database/Mysql/ResultSet.php b/src/Database/Mysql/ResultSet.php
index caf127c..adb7288 100644
--- a/src/Database/Mysql/ResultSet.php
+++ b/src/Database/Mysql/ResultSet.php
@@ -12,17 +12,17 @@ class ResultSet implements IResultSet
         $this->result = $result;
     }
 
-    public function fetch(int $type = IResultSet::FETCH_ASSOC)
+    public function fetch(int $type = IResultSet::FETCH_ASSOC): ?array
     {
         return $this->result->fetch_array($this->convertFetchType($type));
     }
 
-    public function fetchAll(int $type = IResultSet::FETCH_ASSOC)
+    public function fetchAll(int $type = IResultSet::FETCH_ASSOC): array
     {
         return $this->result->fetch_all($this->convertFetchType($type));
     }
 
-    public function fetchOneColumn(string $valueName, string $keyName = null)
+    public function fetchOneColumn(string $valueName, string $keyName = null): array
     {
         $array = [];
 
diff --git a/src/Database/Query/Select.php b/src/Database/Query/Select.php
index 4d32f9b..a379728 100644
--- a/src/Database/Query/Select.php
+++ b/src/Database/Query/Select.php
@@ -115,7 +115,7 @@ class Select
         return $this;
     }
 
-    public function orderBy($column, string $type = 'asc'): Select
+    public function orderBy($column, string $type = 'ASC'): Select
     {
         $this->orders[] = [$column, $type];
 
@@ -394,7 +394,7 @@ class Select
         $orders = $this->orders;
 
         array_walk($orders, function (&$value, $key) {
-            $value = $this->generateColumn($value[0]) . ' ' . $value[1];
+            $value = $this->generateColumn($value[0]) . ' ' . strtoupper($value[1]);
         });
 
         return implode(',', $orders);
diff --git a/src/Interfaces/Database/IResultSet.php b/src/Interfaces/Database/IResultSet.php
index 69d99f5..cf73cd0 100644
--- a/src/Interfaces/Database/IResultSet.php
+++ b/src/Interfaces/Database/IResultSet.php
@@ -8,9 +8,9 @@ interface IResultSet
 
     const FETCH_BOTH = 2;
 
-    public function fetch(int $type);
+    public function fetch(int $type): ?array;
 
-    public function fetchAll(int $type);
+    public function fetchAll(int $type): array;
 
-    public function fetchOneColumn(string $valueName, string $keyName);
+    public function fetchOneColumn(string $valueName, string $keyName): array;
 }