How to avoid duplicate entries with SELECT statement?
SELECT a.*                                -- select all rows
FROM tableX  a                            -- from table
WHERE a.tuser = 1                         -- where either tuser = 1
   OR NOT EXISTS                          -- or there is no other 
      ( SELECT *                          -- row 
        FROM tableX  b                    -- in the table
        WHERE b.tuser = 1                 -- with tuser = 1
          AND b.id = a.id                 -- and same "id",
          AND b.id_user = a.id_user       -- same "id_user"
          AND b.id_word = a.id_word       -- and same "id_word"
      ) ;