diff --git a/lib/Db/AbstractResult.php b/lib/Db/AbstractResult.php
new file mode 100644
index 0000000..dce2926
--- /dev/null
+++ b/lib/Db/AbstractResult.php
@@ -0,0 +1,55 @@
+<?php
+declare(strict_types=1);
+namespace JKingWeb\Arsse\Db;
+
+abstract class AbstractResult implements Result {
+    protected $pos = 0;
+    protected $cur = null;
+
+    // actual public methods
+
+    public function getValue() {
+        $this->next();
+        if ($this->valid()) {
+            $keys = array_keys($this->cur);
+            return $this->cur[array_shift($keys)];
+        }
+        return null;
+    }
+
+    public function getRow() {
+        $this->next();
+        return ($this->valid() ? $this->cur : null);
+    }
+
+    public function getAll(): array {
+        return iterator_to_array($this, false);
+    }
+
+    abstract public function changes();
+
+    abstract public function lastId();
+
+    // PHP iterator methods
+
+    abstract public function valid();
+
+    public function next() {
+        $this->cur = null;
+        $this->pos += 1;
+    }
+
+    public function current() {
+        return $this->cur;
+    }
+
+    public function key() {
+        return $this->pos;
+    }
+
+    public function rewind() {
+        if ($this->pos) {
+            throw new Exception("resultReused");
+        }
+    }
+}
diff --git a/lib/Db/SQLite3/Result.php b/lib/Db/SQLite3/Result.php
index df82390..9aed7a9 100644
--- a/lib/Db/SQLite3/Result.php
+++ b/lib/Db/SQLite3/Result.php
@@ -1,9 +1,10 @@
 <?php
 declare(strict_types=1);
 namespace JKingWeb\Arsse\Db\SQLite3;
+
 use JKingWeb\Arsse\Db\Exception;
 
-class Result implements \JKingWeb\Arsse\Db\Result {
+class Result extends \JKingWeb\Arsse\Db\AbstractResult {
     protected $st;
     protected $set;
     protected $pos = 0;
@@ -13,24 +14,6 @@ class Result implements \JKingWeb\Arsse\Db\Result {
 
     // actual public methods
 
-    public function getValue() {
-        $this->next();
-        if ($this->valid()) {
-            $keys = array_keys($this->cur);
-            return $this->cur[array_shift($keys)];
-        }
-        return null;
-    }
-
-    public function getRow() {
-        $this->next();
-        return ($this->valid() ? $this->cur : null);
-    }
-
-    public function getAll(): array {
-        return iterator_to_array($this, false);
-    }
-
     public function changes() {
         return $this->rows;
     }
@@ -62,23 +45,4 @@ class Result implements \JKingWeb\Arsse\Db\Result {
         $this->cur = $this->set->fetchArray(\SQLITE3_ASSOC);
         return ($this->cur !== false);
     }
-
-    public function next() {
-        $this->cur = null;
-        $this->pos += 1;
-    }
-
-    public function current() {
-        return $this->cur;
-    }
-
-    public function key() {
-        return $this->pos;
-    }
-
-    public function rewind() {
-        if ($this->pos) {
-            throw new Exception("resultReused");
-        }
-    }
 }