Well, I couldn't get a slick solution, so I did a hack:
- Created a new integer field called
rand_inst
. - Assign a random number to each empty slot.
- Update
rand_inst
to be the instance number of that random number within this household. E.g., if I get two 3's, then the second 3 will haverand_inst
set to 2. - Update the table to assign a different random number anywhere that
rand_inst>1
. - Repeat assignment and update until we converge on a solution.
Here's what it looks like. Too lazy to anonymise it, so the names are a little different from my original post:
/* Iterative hack to fill 6 slots with a random number between 1 and 13.
A random number *must not* repeat within a household_id.
*/
update c3_lalfinal a
set a.rand_inst = b.rnum
from (
select household_id
,slot_nbr
,row_number() over (partition by household_id,rnd order by null) as rnum
from c3_lalfinal
) b
where a.household_id = b.household_id
and a.slot_nbr = b.slot_nbr
;
update c3_lalfinal
set rnd = CAST(0.5 + random() * (13-1+1) as INT)
where rand_inst>1
;
/* Repeat until this query returns 0: */
select count(*) from (
select household_id from c3_lalfinal group by 1 having count(distinct(rnd)) <> 6
) x
;