Redirects to non-existant pages

SQL

SELECT CONCAT('https://en.wikipedia.org/wiki/', CASE page_namespace
                WHEN   -2 THEN 'Media:'             WHEN   -1 THEN 'Special:'
                WHEN    0 THEN ''                   WHEN    1 THEN 'Talk:'
                WHEN    2 THEN 'User:'              WHEN    3 THEN 'User talk:'
                WHEN    4 THEN 'Wikipedia:'         WHEN    5 THEN 'Wikipedia talk:'
                WHEN    6 THEN ':File:'             WHEN    7 THEN 'File talk:'
                WHEN    8 THEN 'MediaWiki:'         WHEN    9 THEN 'MediaWiki talk:'
                WHEN   10 THEN 'Template:'          WHEN   11 THEN 'Template talk:'
                WHEN   12 THEN 'Help:'              WHEN   13 THEN 'Help talk:'
                WHEN   14 THEN ':Category:'         WHEN   15 THEN 'Category talk:'
                WHEN  100 THEN 'Portal:'            WHEN  101 THEN 'Portal talk:'
                WHEN  108 THEN 'Book:'              WHEN  109 THEN 'Book talk:'
                WHEN  118 THEN 'Draft:'             WHEN  119 THEN 'Draft talk:'
                WHEN  446 THEN 'Education Program:' WHEN  447 THEN 'Education Program talk:'
                WHEN  710 THEN 'TimedText:'         WHEN  711 THEN 'TimedText talk:'
                WHEN  828 THEN 'Module:'            WHEN  829 THEN 'Module talk:'
                WHEN 2300 THEN 'Gadget:'            WHEN 2301 THEN 'Gadget talk:'
                WHEN 2302 THEN 'Gadget definition:' WHEN 2303 THEN 'Gadget definition talk:'
                ELSE CONCAT('{{ns:', page_namespace, '}}:')
              END,
              page_title) AS url,
              CONCAT('https://en.wikipedia.org/wiki/', CASE rd_namespace
                WHEN   -2 THEN 'Media:'             WHEN   -1 THEN 'Special:'
                WHEN    0 THEN ''                   WHEN    1 THEN 'Talk:'
                WHEN    2 THEN 'User:'              WHEN    3 THEN 'User talk:'
                WHEN    4 THEN 'Wikipedia:'         WHEN    5 THEN 'Wikipedia talk:'
                WHEN    6 THEN ':File:'             WHEN    7 THEN 'File talk:'
                WHEN    8 THEN 'MediaWiki:'         WHEN    9 THEN 'MediaWiki talk:'
                WHEN   10 THEN 'Template:'          WHEN   11 THEN 'Template talk:'
                WHEN   12 THEN 'Help:'              WHEN   13 THEN 'Help talk:'
                WHEN   14 THEN ':Category:'         WHEN   15 THEN 'Category talk:'
                WHEN  100 THEN 'Portal:'            WHEN  101 THEN 'Portal talk:'
                WHEN  108 THEN 'Book:'              WHEN  109 THEN 'Book talk:'
                WHEN  118 THEN 'Draft:'             WHEN  119 THEN 'Draft talk:'
                WHEN  446 THEN 'Education Program:' WHEN  447 THEN 'Education Program talk:'
                WHEN  710 THEN 'TimedText:'         WHEN  711 THEN 'TimedText talk:'
                WHEN  828 THEN 'Module:'            WHEN  829 THEN 'Module talk:'
                WHEN 2300 THEN 'Gadget:'            WHEN 2301 THEN 'Gadget talk:'
                WHEN 2302 THEN 'Gadget definition:' WHEN 2303 THEN 'Gadget definition talk:'
                ELSE CONCAT('{{ns:', rd_namespace, '}}:')
              END,
              rd_title) AS rd_url
  FROM page, redirect
 WHERE page_id = rd_from
   AND rd_interwiki = ''
   AND rd_namespace >= 0
   AND rd_namespace != 6
   AND rd_title NOT IN (SELECT page_title FROM page WHERE page_namespace = rd_namespace)
SQL

Checking query status...
