diff --git a/src/Pixie/QueryBuilder/Adapters/BaseAdapter.php b/src/Pixie/QueryBuilder/Adapters/BaseAdapter.php
index a6277df..98cb96b 100644
--- a/src/Pixie/QueryBuilder/Adapters/BaseAdapter.php
+++ b/src/Pixie/QueryBuilder/Adapters/BaseAdapter.php
@@ -212,7 +212,7 @@ public function replace($statements, array $data)
     {
         return $this->doInsert($statements, $data, 'REPLACE');
     }
-
+    
     /**
      * Build fields assignment part of SET ... or ON DUBLICATE KEY UPDATE ... statements
      *
@@ -224,7 +224,6 @@ private function getUpdateStatement($data)
     {
         $bindings = array();
         $statement = '';
-
         foreach ($data as $key => $value) {
             if ($value instanceof Raw) {
                 $statement .= $this->wrapSanitizer($key) . '=' . $value . ',';
@@ -233,7 +232,6 @@ private function getUpdateStatement($data)
                 $bindings[] = $value;
             }
         }
-
         $statement = trim($statement, ',');
         return array($statement, $bindings);
     }
@@ -406,7 +404,7 @@ protected function buildCriteria($statements, $bindValues = true)
                         break;
                 }
             } elseif ($value instanceof Raw) {
-                $criteria .= "{$statement['joiner']} {$key} {$statement['operator']} $value";
+                $criteria .= "{$statement['joiner']} {$key} {$statement['operator']} $value ";
             } else {
                 // Usual where like criteria
 
diff --git a/src/Pixie/QueryBuilder/QueryBuilderHandler.php b/src/Pixie/QueryBuilder/QueryBuilderHandler.php
index 7f89796..23334e0 100644
--- a/src/Pixie/QueryBuilder/QueryBuilderHandler.php
+++ b/src/Pixie/QueryBuilder/QueryBuilderHandler.php
@@ -48,6 +48,11 @@ class QueryBuilderHandler
      * @var array
      */
     protected $fetchParameters = array(\PDO::FETCH_OBJ);
+    
+    /**
+     * @var integer
+     */
+    protected $transactions = 0;
 
     /**
      * @param null|\Pixie\Connection $connection
@@ -788,20 +793,66 @@ public function join($table, $key, $operator = null, $value = null, $type = 'inn
 
         return $this;
     }
-
-    public function transaction(\Closure $callback)
+    
+    /**
+     * @return void
+     */
+    public function beginTransaction() 
     {
-        try {
+        ++$this->transactions;
+        
+        if ($this->transactions === 1) {
             $this->pdo->beginTransaction();
-
-            $callback($this);
+        }
+    }
+    
+    /**
+     * @return void
+     */
+    public function commit() 
+    {
+        if ($this->transactions === 1) {
             $this->pdo->commit();
+        }
+        
+        --$this->transactions;
+    }
+    
+    /**
+     * @return void
+     */
+    public function rollback() 
+    {
+        if ($this->transactions == 1) {
+            $this->transactions = 0;
+            $this->pdo->rollBack();
+        }
+        else {
+            --$this->transactions;
+        }
+    }
+    
+    /**
+     * @param \Closure $callback
+     *
+     * @return mixed
+     *
+     * @throws \Exception
+     */
+    public function transaction(\Closure $callback)
+    {
+        try {
+            $this->beginTransaction();
 
-            return true;
+            $result = $callback($this);
+            $this->commit();
         } catch (\Exception $e) {
-            $this->pdo->rollBack();
-            return false;
+            $this->rollback();
+            
+            throw $e;
         }
+        
+        return $result;
     }
 
     /**