Subqueries: Any/All

1. Subquery Any

Syntax:

-- any
-- remove inner order by
select EnglishProductName, ListPrice from DimProduct
where ListPrice > any(select avg(ListPrice) from DimProduct
group by ProductSubcategoryKey)
order by ListPrice asc

Analysis:

It’s asking for a list of products whose price is greater than any of the average list prices from the subquery. In this case, the lowest average is 7.95. Therefore it’s showing all of those products with a ListPrice of more than 7.95.

2. Subquery All

Syntax:

-- all with nulls
select EnglishProductName, ListPrice from DimProduct
where ListPrice > all(select avg(ListPrice) from DimProduct
group by ProductSubcategoryKey)
order by ListPrice asc

Analysis:

It’s looking for all products with a price greater than all of the average prices from the subquery. In other words, it’s looking for all those productes whose price is greater than the highest of the subcategory average prices.

Caution:

Do not let null value join into the comparison, otherwise, you will get incorrect results.

But there was an average price with a null value, A null value, if you like, is indeterminate --- so it cannot be guaranteed to really be the maximum. The maximum is unknown, so the outer query fails to show any records.

Solution:

Adding a Having clause to the subquery --- this is going to eliminate all average prices with null values.

-- all without nulls
select EnglishProductName, ListPrice from DimProduct
where ListPrice > all(select avg(ListPrice) from DimProduct group by 
ProductSubcategoryKey having avg(ListPrice) is not null)
order by ListPrice asc