SELECT concat( "[https://en.wikipedia.org/w/index.php?title=User:{{urlencode:",

              p.page_title, "}}&redirect=no User:", p.page_title, "]" )

AS "Redirects from nonexistent user, except user subpages, to mainspace"

FROM redirect r

INNER JOIN page p ON p.page_id = r.rd_from

WHERE p.page_namespace = 2

AND   r.rd_namespace = 0

AND   p.page_title NOT LIKE '%/%'

INTERSECT

SELECT concat( "[https://en.wikipedia.org/w/index.php?title=User:{{urlencode:",

              p.page_title, "}}&redirect=no User:", p.page_title, "]" )

AS "Redirects from nonexistent user, except user subpages, to mainspace"

FROM page p

LEFT JOIN `user`u ON u.user_name = REPLACE(SUBSTRING_INDEX(p.page_title, '/', 1), '_', ' ')

WHERE u.user_name IS NULL

AND p.page_is_redirect = 1;