Question

I am attempting to get a value from a table based on “Preference”.

I have a table “t1” including two columns “id” and “alphabet”

Sample data

1 A
1 B
2 A
3 A
3 B

It means every id has the default value “A” and some have “B”).

Now I would like to get the values of “id” based on preference of “B”. Thus, if an ID has both A and B, I want the B row. If no B row is found, then the default A should be returned.

Answer 1

This might be slightly off as mysql dialect always throws me. Since B falls after A in an alphabetical sort, if you group on the ID and then select the maximum, it will give you all the B rows where they exist, otherwise you will get the A row.

SELECT
    ID,
    MAX(alphabet) AS preference
FROM
    t1
GROUP BY
    ID

Now, if your data is more complex than what you’ve indicated, you will need to examine whether the MAX logic still applies.