Re: Confused about CASE

> I wanted to use the following statement to "translate" the relkind
> column to a
> more descriptive value:
>
> select c.relname
> case
> when c.relkind in ('t','r') then 'table'
> when c.relkind = 'i' then 'index'
> when c.relkind = 'S' then 'sequence'
> when c.relkind = 'v' then 'view'
> else c.relkind
> end as mykind
> from pg_class c
> ;
>
> The idea is that for anything else than 't', 'r', 'i', 'S' or 'v' it
> should
> simply return the value of relkind. In the other cases I want "my"
> value.
>
> But for some reason this returns the value of relkind for all rows.
> When I
> remove the "else c.relkind" part, it works as expected.

I agree, this seems confusing. I found a section of the doc that caught my
eye:

"The data types of all the result expressions must be convertible to a
single output type."

Which led me to try this, which works:

select c.relname,
case
when c.relkind in ('t','r') then 'table'
when c.relkind = 'i' then 'index'
when c.relkind = 'S' then 'sequence'
when c.relkind = 'v' then 'view'
else c.relkind::text
end as mykind
from pg_class c