SQL Select statement from multiple tables while adding values - mysql

Question

I'm having a bit of trouble figuring out a good statement to write. I am able to achieve what I want when I query a specific 'Company' but I wanting to get the values for all of the companies in the database.
Basically I have 3 tables: Users, Companies, Plans_ExchangeMailbox. What I need to do is query how many plans are in use for each company. The plans are assigned at the user level in the users table.
Here is my table layouts:
USERS
DisplayName
CompanyCode (This is the ID from the CompanyCode in the Companies table)
MailboxPlan (This is the ID from the Plans_ExchangeMailbox Table)
Companies
CompanyName
CompanyCode
Plans_ExchangeMailbox
MailboxPlanName
MailboxPlanID
Here is the format I am looking to generate:
CompanyName, MailboxPlanName, Count (this is the number of MailboxPlanID for a company)
I was able to get this working but the problem is it can only do one company at a time and it doesn't get the CompanyName:
SELECT
Plans_ExchangeMailbox.MailboxPlanName,
SUM(CASE WHEN Users.MailboxPlan = Plans_ExchangeMailbox.MailboxPlanId THEN 1 ELSE 0 END) AS PlanCount
FROM
Plans_ExchangeMailbox, Users
WHERE
Users.CompanyCode='CC0'
GROUP BY
Plans_ExchangeMailbox.MailboxPlanName
The Final Format How it Should Be:
Headers: CompanyName, PlanName, Count
Values:
Microsoft, Bronze Plan, 5
Microsoft, Gold Plan, 20
Dell, Bronze Plan, 3
Dell, Silver Plan, 80
etc.....

Answer 1

Try this:
SELECT
C.CompanyName,
E.MailboxPlanName,
COUNT(1) Cnt
FROM Companies C
JOIN Users U
ON C.CompanyCode = U.CompanyCode
JOIN Plans_ExchangeMailbox E
ON U.MailboxPlan = E.MailboxPlanID
GROUP BY
C.CompanyCode,
C.CompanyName,
E.MailboxPlanID,
E.MailboxPlanName
Grouped by C.CompanyCode and E.MailboxPlanID in case if there are different companies or MailboxPlan with same name. If no,you can remove them from GROUP BY clause.