SQLite 3.27

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select sqlite_version();


sqlite_version()


3.27.2


CREATE TABLE x ( name, surname, nickname );
✓
INSERT INTO x
        SELECT 'Jeniffer',  'Doe',         'Jenny' UNION ALL
        SELECT 'Jeniffer',  'Doe',         NULL    UNION ALL
        SELECT 'Jeniffer',  'Doe',         'Jenny'
;
✓
SELECT * FROM x;


name
surname
nickname


Jeniffer
Doe
Jenny

Jeniffer
Doe
null

Jeniffer
Doe
Jenny


SELECT DISTINCT x.*
  FROM x
 WHERE NOT EXISTS (
           SELECT 1 FROM x AS x1
            WHERE (x.name,  x.surname) = (x1.name,  x1.surname)
              AND COALESCE(x.nickname, x1.nickname || 'x')
                > COALESCE(x1.nickname, x.nickname || 'x')
       )
;


name
surname
nickname


Jeniffer
Doe
Jenny


select x.* 
  from (
         select x.*
              , row_number() over (partition by name, surname order by nickname is null, nickname) as seqnum
           from x
       ) AS x
 where seqnum = 1
;


name
surname
nickname
seqnum


Jeniffer
Doe
Jenny
1