modifications to db updated

sails/conf/pictodb.sql

@@ -389,7 +389,8 @@ CREATE TABLE IF NOT EXISTS `stu_picto` (
   `attributes` varchar(1000) COLLATE utf8_unicode_ci DEFAULT NULL COMMENT 'JSON object describing the properties of the picto according to the properties defined in meta_picto',
   PRIMARY KEY (`id`),
   KEY `fk_picto` (`id_pic`),
-  KEY `id_stu` (`id_stu`)
+  KEY `id_stu` (`id_stu`), 
+  UNIQUE `uq_stupicto` (`id_stu`,`id_pic`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;
 
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