MDL-14679 dml/native_mysqli fixed sql concat

diff --git a/lib/dml/mysqli_native_moodle_database.php b/lib/dml/mysqli_native_moodle_database.php
index 1acb4b6bfaa8a8e2b7c289419773ee80f4a51daa..b21f95c8234aa3572449d9f632b23ea2807ce4f6 100644 (file)
--- a/lib/dml/mysqli_native_moodle_database.php
+++ b/lib/dml/mysqli_native_moodle_database.php
@@ -853,7 +853,7 @@ class mysqli_native_moodle_database extends moodle_database {
         $arr = func_get_args();
         $s = implode(',', $arr);
         if ($s === '') {
-            //TODO: error
+            return "''";
         }
         return "CONCAT($s)";
     }
@@ -864,7 +864,7 @@ class mysqli_native_moodle_database extends moodle_database {
         }
         $s = implode(',', $elements);
         if ($s === '') {
-            //TODO: error
+            return "''";
         }
         return "CONCAT ($s)";
     }