From 21828e1a5d8834b8286fe37424accd5a46c9b208 Mon Sep 17 00:00:00 2001
From: Walther Lalk <walther@octoplus.co.za>
Date: Fri, 8 Aug 2014 16:17:17 +0200
Subject: [PATCH] Only add 'day' once with SqlServer DATEDIFF

If a single instance of a DATEDIFF Expression was used more than once, 'day' would be added multiple times (Once be usage). This threw an SQLServer error.
---
 src/Database/Dialect/SqlserverDialectTrait.php | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/Database/Dialect/SqlserverDialectTrait.php b/src/Database/Dialect/SqlserverDialectTrait.php
index e2e2aedd745..a8916970d73 100644
--- a/src/Database/Dialect/SqlserverDialectTrait.php
+++ b/src/Database/Dialect/SqlserverDialectTrait.php
@@ -155,7 +155,18 @@ protected function _transformFunctionExpression(FunctionExpression $expression)
 				$expression->name('')->type(' +');
 				break;
 			case 'DATEDIFF':
-				$expression->add(['day' => 'literal'], [], true);
+				$hasDay = false;
+				$visitor = function($value) use (&$hasDay){
+					if ($value === 'day') {
+						$hasDay = true;
+					}
+					return $value;
+				};
+				$expression->iterateParts($visitor);
+
+				if (!$hasDay) {
+					$expression->add(['day' => 'literal'], [], true);
+				}
 				break;
 			case 'CURRENT_DATE':
 				$time = new FunctionExpression('GETUTCDATE');