Select Distinct Rows with complex criteria

I have a table generated from a CRM software and it has a lot of repited individuals in different rows but with different fields completed in each repetition, something like this:

id	birth_date	sex	postal_code	customer	smoker
001	NULL	NULL	00067	Yes	1
001	NULL	Male	00067	NULL	1
001	21/03/1994	NULL	00067	NULL	NULL
002	NULL	Female	NULL	NULL	NULL
002	NULL	NULL	09986	No	0
003	13/01/1986	NULL	NULL	No	1

The desired table extracted from this one should be this:

id	birth_date	sex	postal_code	customer	smoker
001	21/03/1994	Male	00067	Yes	1
002	NULL	Female	09986	No	0
003	13/01/1986	NULL	NULL	No	1

So as you can see, there are some columns completed in some repetitions, so the idea is to avoid repetitions (here we see a repetition because there’s the same id for more than one row, the id column should be the primary key) and get the maximum information about that id.

Any idea of how to achieve that?

Answer

You can aggregate the rows and take the max non-null value, as in:

select
  id,
  max(birth_date) as birth_date,
  max(sex) as sex,
  max(postal_code) as postal_code,
  max(customer) as customer,
  max(smoker) as smoker
from t
group by id

Now, this solution won’t account for inconsistent data when, for example, the same person has two different birth dates.