fix syntax

src/main/scala/com/gmei/data/dq/pvCheker.scala

@@ -41,7 +41,7 @@ object pvCheker {
     val df = sc.sql(s"""
       select
         cl_id, action, cl_type, app_version,
-        case when params['page_name'] is null then 'NULL' else params['page_name'],
+        case when params['page_name'] is null then 'NULL' else params['page_name'] end as page_name,
         case when params['extra_param'] is null then 0 else 1 end as extra,
         case
           when params['referrer'] is null then -1