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# TOP 2 results in just one query

The following query lists the number of customers in each state:

```SELECT state, COUNT(*) AS customers
FROM customer GROUP BY state
ORDER BY customers DESC```

From this query I want to get the maximum number of customers and the second most number of customers in just one single query. I have tried using max(customers) and methods similar to this but violates the SQL syntax. How am I to do this all in one query?

If your database is Microsoft SQL Server or Access, you should use the TOP keyword:

```select top 2
state
, count(*) as customers
from customer
group by state
order by customers desc```

If your database is MySQL or PostgreSQL, you should use the LIMIT keyword:

```select state
, count(*) as customers
from customer
group by state
order by customers desc
limit 2```

If your database is Oracle, you can use ROWNUM from a subselect:

```select state
, customers
from ( select state
, count(*)
as customers
from customer
group by state
order by customers desc )
where rownum <= 2```

All of the above are likely more efficient than the generic "top n" approach. The generic "top n" query looks like this, assuming you want the top 2:

```select foo
, bar
from sometable xxx
where 2 >
( select count(*)
from sometable
where bar > xxx.bar
)
order by bar desc```

What the subquery does is count the number of rows that have a higher value than the value of the row of the outer query; if that number is less than two, then that row is one of the top two.

Applied to your problem, we have to use a derived table, since the values we're evaluating are counts themselves:

```select state
, customers
from ( select state
, count(*)
as customers
from customer
group by state ) xxx
where 2 >
( select count(*)
from ( select state
, count(*)
as customers
from customer
group by state  )
where customers > xxx.customers
)
order by customers desc```

This was last published in October 2002

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