WITH CTE AS (
SELECT *
,row_number() OVER(PARTITION BY word, num ORDER BY id) AS row_num
FROM dupes
)
SELECT word, num, id
FROM cte
WHERE row_num = 1
ORDER BY word, num;
/*
word|num|id|
----|---|--|
aaa |100| 1|
bbb |200| 2|
bbb |400| 4|
ccc |300| 3|
ddd |400| 7|
*/