Question

I have a table as follow:

user_id value1 value2 value3 value4
1       2      3      4      null
2       null   5      2      null
3       null   null   100    3
...

Now I want to get the minimum of value1, value2, value3 and value4 and then return the user_id with the highest minimum.

I thought about using least and then group by descending, but how do I efficiently check for null?
The output for the table would be:

user_id value
3       3
1       2
2       2

Answer 1

~0>>1 will give you the biggest BigInt value in mysql (should be enough)

coalesce(
      nullif(
           least(coalesce(value1, ~0>>1), coalesce(value2, ~0>>1),
                 coalesce(value3, ~0>>1), coalesce(value4, ~0>>1)), 
      ~0>>1), 
0)

or you have to do combinations (I put them all, not sure it’s necessary)

coalesce
    (least(
       coalesce(value1, value2, value3, value4), 
       coalesce(value1, value2, value4, value3),
       coalesce(value1, value3, value2, value4),
       coalesce(value1, value3, value4, value2),
       coalesce(value1, value4, value2, value3),
       coalesce(value1, value4, value3, value2),
       coalesce(value2, value1, value3, value4),
       coalesce(value2, value1, value4, value3),
       coalesce(value2, value3, value1, value4),
       coalesce(value2, value3, value4, value1),
       coalesce(value2, value4, value1, value3),
       coalesce(value2, value4, value3, value1),
       coalesce(value3, value1, value2, value4),
       coalesce(value3, value1, value4, value2),
       coalesce(value3, value2, value1, value4),
       coalesce(value3, value2, value4, value1),
       coalesce(value3, value4, value1, value2),
       coalesce(value3, value4, value2, value1),
       coalesce(value4, value1, value2, value3),
       coalesce(value4, value1, value3, value2),
       coalesce(value4, value2, value1, value3),
       coalesce(value4, value2, value3, value1),
       coalesce(value4, value3, value1, value2),
       coalesce(value4, value3, value2, value1)
)

, 0)