跨多个表进行分组

Question

I am trying to get individual counts for multiple table join results.

I have a table of several divisions that should be joined to a table of dealers, which in turn, should be joined to a table of all the transactions by those dealers. I want to show how many dealer and transactions there are per division.

The following query returns the total number of transactions for both the transactionCount and the dealerCount , instead of unique values for each.

SELECT
    d.*,
    COUNT(dlr.id) AS dealerCount,
    COUNT(t.id) AS transactionCount
FROM
    division AS d
INNER JOIN
    dealers AS dlr ON dlr.division = d.id
INNER JOIN
    transactions AS t ON t.dealer_code = dlr.dealer_code
GROUP BY
    d.id

Answer 1

I haven't tested this, but what about using

count(distinct dlr.id)

in your select?