Postgress by a CASE with DISTINCT in select - postgresql

Question

I have a query like below getting the error - 'SELECT DISTINCT, ORDER BY expressions must appear in select list'
select distinct name
from fruits
order by case
when name = 'mango' then 1
else 2
end
This results 4 records, say
apple, mango, pear and grape
How can I make sure I get Mango as the first record always and the rest follow. I tried using the case statement, but not able to get the desired results. Any ideas will be appreciated.

Answer 1

I believe this should accomplish what you describe as needing.
select distinct
name,
case name when 'Mango' then 1 else 2 end as fruitOrder
from fruits
order by
fruitOrder

Answer 2

If you need to always have 'mango' in first position, no matter the other rows, this could be a way:
with fruits(name) as (
select 'apple' from dual union all
select 'mango' from dual union all
select 'pear' from dual union all
select 'grape' from dual
)
select name
from fruits
order by case
when name = 'mango' then 1
else 2
end
If you need to add a DISTINCT, this should work:
select distinct name,
case
when name = 'mango' then 1
else 2
end orderCol
from fruits
order by orderCol

Answer 3

This will give you 'Mango' followed by the others in order;
WITH get_rows AS
(SELECT DISTINCT item_type
FROM the_item)
SELECT item_type
FROM
(SELECT 1 as seq, item_type
FROM get_rows
WHERE item_type = 'Mango'
UNION ALL
SELECT 2 as seq, item_type
FROM get_rows
WHERE item_type <> 'Mango')
ORDER BY seq, item_type