diff --git a/adminer/drivers/mssql.inc.php b/adminer/drivers/mssql.inc.php
index 033a09b2..5dc15a5c 100644
--- a/adminer/drivers/mssql.inc.php
+++ b/adminer/drivers/mssql.inc.php
@@ -187,27 +187,28 @@ if (isset($_GET["mssql"])) {
 
 		function insertUpdate($table, $rows, $primary) {
 			$fields = fields($table);
+			$update = array();
+			$where = array();
+			$set = reset($rows);
+			$columns = "c" . implode(", c", range(1, count($set)));
+			$c = 0;
+			foreach ($set as $key => $val) {
+				$c++;
+				$name = idf_unescape($key);
+				if (!$fields[$name]["auto_increment"]) {
+					$update[] = "$key = c$c";
+				}
+				if (isset($primary[$name])) {
+					$where[] = "$key = c$c";
+				}
+			}
 			$values = array();
 			foreach ($rows as $set) {
-				$update = array();
-				$where = array();
-				$columns = "c" . implode(", c", range(1, count($set)));
-				$c = 0;
-				foreach ($set as $key => $val) {
-					$c++;
-					$name = idf_unescape($key);
-					if (!$fields[$name]["auto_increment"]) {
-						$update[] = "$key = c$c";
-					}
-					if (isset($primary[$name])) {
-						$where[] = "$key = c$c";
-					}
-				}
 				$values[] = "(" . implode(", ", $set) . ")";
 			}
 			queries("SET IDENTITY_INSERT " . table($table) . " ON");
 			$return = queries("MERGE " . table($table) . " USING (VALUES\n\t" . implode(",\n\t", $values) . "\n) AS source ($columns) ON " . implode(" AND ", $where) //! source, c1 - possible conflict
-				. "\nWHEN MATCHED THEN UPDATE SET " . implode(", ", $update)
+				. ($update ? "\nWHEN MATCHED THEN UPDATE SET " . implode(", ", $update) : "")
 				. "\nWHEN NOT MATCHED THEN INSERT (" . implode(", ", array_keys($set)) . ") VALUES ($columns);" // ; is mandatory
 			);
 			queries("SET IDENTITY_INSERT " . table($table) . " OFF");