Question

Let’s say I have a SQL table like this:

UniqueID  Word
1         apple
2         orange
3         banana
4         apple

I want to create a hash key as an integer. That integer should map to a particular word. So that the key has some meaning, I’d like the number to be the UniqueID of the first occurance of word. Which means I’d like to generate a table like this:

Unique ID  Word    WordHash
1          apple   1
2          orange  2
3          banana  3
4          apple   1

I tried using a group by statement, along with min(unique id), but that gets rid of the last apple row. I’d like to keep that row.

Answer 1

SELECT t.UniqueID, t.Word, q.MinID AS WordHash
    FROM YourTable t
        INNER JOIN (SELECT Word, MIN(UniqueID) AS MinID
                        FROM YourTable
                        GROUP BY Word) q
            ON t.Word = q.Word