如何在SQL查询中使用min作为条件

Question

cat use min as condition

the where statement is where it breaks but i cant fix it

select category, count(*) as number_of_cats
from books
where number_of_cats > min(number_of_cats)
group by category
order by category;

Answer 1

Having + sub-query

select category, count(*) as number_of_books
from books
group by category
having count(*) >     -- check the one whose count is STRICTLY greater then minimum
                      (  select min (st.t) -- find the minimum of all categories
                         from
                         ( select count(*) as t --find the count for all categories
                           from books
                           group by category
                                    ) st -- an alias to avoid parsing errors
                          )

Another option, but with this solution in case of ex-aequo only first category is removed:

select select category, count(*) as number_of_books
    from books
    where category not in (select bb.category 
                           from books bb
                           group by bb.category 
                           order by count(*) asc
                           limit 1)
    group by category

Answer 2

You could use common table expressions here, eg:

WITH CategoryCount AS (
    SELECT 
        category, 
        COUNT(*) AS number_of_books
    FROM
        books
    GROUP BY 
        category),
MinBooks AS (
    SELECT
        MIN(number_of_books) AS min_number_of_books
    FROM
        CategoryCount)
SELECT
    cc.*
FROM
    CategoryCount cc
    CROSS JOIN MinBooks m
WHERE
    cc.number_of_books > m.min_number_of_books;