Merge pull request #745 from zeroedin-bill/sqlserver-2012-offset-limit

Added doModifyLimitQuery for SQLServer2012Platform that uses OFFSET... FETCH

lib/Doctrine/DBAL/Platforms/SQLServer2012Platform.php

@@ -24,7 +24,8 @@ use Doctrine\DBAL\Schema\Sequence;
 /**
  * Platform to ensure compatibility of Doctrine with Microsoft SQL Server 2012 version.
  *
- * Differences to SQL Server 2008 and before are that sequences are introduced.
+ * Differences to SQL Server 2008 and before are that sequences are introduced,
+ * and support for the new OFFSET... FETCH syntax for result pagination has been added.
  *
  * @author Steve Müller <st.mueller@dzh-online.de>
  */
@@ -102,4 +103,41 @@ class SQLServer2012Platform extends SQLServer2008Platform
     {
         return 'Doctrine\DBAL\Platforms\Keywords\SQLServer2012Keywords';
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function doModifyLimitQuery($query, $limit, $offset = null)
+    {
+        if ($limit === null && $offset === null) {
+            return $query;
+        }
+
+        // Queries using OFFSET... FETCH MUST have an ORDER BY clause
+        // Find the position of the last instance of ORDER BY and ensure it is not within a parenthetical statement
+        $orderByPos = strripos($query, " ORDER BY ");
+        
+        if ($orderByPos === false
+            || substr_count($query, "(", $orderByPos) - substr_count($query, ")", $orderByPos)
+        ) {
+            // In another DBMS, we could do ORDER BY 0, but SQL Server gets angry if you use constant expressions in
+            // the order by list.
+            $query .= " ORDER BY (SELECT 0)";
+        }
+
+        if ($offset === null) {
+            $offset = 0;
+        }
+
+        // This looks somewhat like MYSQL, but limit/offset are in inverse positions
+        // Supposedly SQL:2008 core standard.
+        // Per TSQL spec, FETCH NEXT n ROWS ONLY is not valid without OFFSET n ROWS.
+        $query .= " OFFSET " . (int) $offset . " ROWS";
+
+        if ($limit !== null) {
+            $query .= " FETCH NEXT " . (int) $limit . " ROWS ONLY";
+        }
+
+        return $query;
+    }
 }