How can I count() on multiple tables in a single query?

[Daevid Vincent]

Using mysql v4.0.x on linux.

Given three tables...

CREATE TABLE Departments (
  DeptID int(10) unsigned NOT NULL auto_increment,
  DeptName char(30) default NULL,
  PRIMARY KEY  (DeptID)
)

CREATE TABLE UserDept (
  CoreID int(10) unsigned NOT NULL default '0',
  DeptID int(10) unsigned NOT NULL default '0',
  DeptAdmin char(1) default NULL,
  DeptEmail char(1) default NULL,
  DeptContact char(1) default NULL,
  KEY DeptID (DeptID),
  KEY CoreID (CoreID)
)

CREATE TABLE IP_Dept (
  IP_Addr int(10) unsigned NOT NULL default '0',
  DeptID int(10) unsigned NOT NULL default '0',
  UNIQUE KEY DeptIP (IP_Addr,DeptID)
)

What I want is a listing of all the department names, and a tally of how
many users in each, and another column with the tally of how many IPs in
each

I've tried various combinations of this, changing the COUNT() and GROUP BY
values:

SELECT 
        Departments.DeptID, DeptName, COUNT(UserDept.CoreID) AS users,
COUNT(IP_Addr) as devices
FROM  Departments 
         LEFT JOIN IP_Dept on Departments.DeptID = IP_Dept.DeptID
          LEFT JOIN UserDept ON Departments.DeptID = UserDept.DeptID 
GROUP BY 
        UserDept.CoreID, IP_Dept.IP_Addr 
ORDER BY 
        DeptName DESC;

But nothing is working right. Mostly what happens is both 'users' and
'devices' is the same value. Is this possible? I can do it for the first
COUNT(). And then I could do a second query, but I'm trying to do this in a
single query if possible.


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