MySQL select 总计在一个不同的查询中

Question

I would like to get a total number of transactions per customer (company). How can I add to this query a counter to calculate the number of records in the transaction table per Company?

select DISTINCT c.CompanyName, c.ContactEmail
From Transactions tr
JOIN Tenants t on tr.tenantid = t.tenantid
JOIN Properties p on t.propertyid = p.propertyid
JOIN Company c on c.companyid = p.companyid

Thanks

Answer 1

Use GROUP BY :

SELECT c.CompanyName, c.ContactEmail, COUNT(*)
FROM Transactions tr JOIN
     Tenants t ON tr.tenantid = t.tenantid
     Properties p ON t.propertyid = p.propertyid
     Company c ON c.companyid = p.companyid
GROUP BY c.CompanyName, c.ContactEmail;

Answer 2

SELECT DISTINCT c.CompanyName, c.ContactEmail, COUNT(tr.id) total_tranactions From Transactions tr JOIN Tenants t on tr.tenantid = t.tenantid JOIN Properties p on t.propertyid = p.propertyid JOIN Company c on c.companyid = p.companyid GROUP BY c.CompanyName, c.ContactEmail;

user primary key of your transaction table in count COUNT() aggregate function.