[sqlite] Problem with distinct select query

[Gary Baranzini]

Hi,

I have a query where I select 20 random distinct rows.

SELECT DISTINCT formulas.pinyin, formulas.majorcategory, 
majorfcategory.item_name
FROM formulas
JOIN majorfcategory ON majorfcategory.id=formulas.majorcategory
ORDER BY RANDOM() LIMIT 20

Each row contains a major category id, ?majorcategory?
I want to improve on this query so that the select will NOT return 
duplicate major categories

I thought I could do:

SELECT DISTINCT formulas.pinyin, formulas.majorcategory, 
majorfcategory.item_name
FROM formulas
JOIN majorfcategory ON majorfcategory.id=formulas.majorcategory
WHERE formulas.majorcategory in (SELECT DISTINCT formulas.majorcategory 
FROM formulas) ORDER BY RANDOM() LIMIT 20

But that doesn?t work.

Any suggestions will be greatly appreciated.

jb