MySQL连接表用于具有多个条件的计数

Question

Trying to create a report across 3 tables - company, account, user. For each company, there's an ID in account. Each user has an account. I can get totals easily enough, but I need to add count of how many users out of the total are registered (username is not null).

SELECT c.c_name, c.c_groupnumber, count(a.a_userid) AS TotalCount
FROM company c
LEFT JOIN account a ON c.c_groupnumber = a.a_groupnumber
WHERE a.a_deleted IS NULL
GROUP BY c.c_groupnumber
HAVING TotalCount > 0;

How can I add in a condition that gives me a count of user.u_username not null while maintaining my TotalCount? The link between account and user is

a.a_userid = user.u_userid

tbl.company
c_id, c_groupnumber, c_name
  1    1234          widgets, inc.
  2    5678          joe's garage

tbl.user
u_userid, u_username, u_name
  1        bill       Bill Smith
  2        frank      Frank Johnson
  3        NULL       Jane Doe
  4        mary       Mary Stack
  5        NULL       Steve Spot

tbl.account
a_id, a_userid, a_groupnumber
 100       1      1234
 101       2      5678
 102       3      5678
 103       4      1234
 104       5      1234

So using the above very simplified table example, company "Widget's Inc." has 3 employees (bill smith, mary stack and steve spot), and of those 3 2 have registered (bill and mary), while steve has not (username is null).

Joe's Garage has 2 employees - Frank and Jane, and Frank has registered, while Jane has not.

I'd love to generate a report something like this:

Group      Company     Total Emp      Reg Emp
1234       Widgets Inc     3              2
5678       Joe's Garag     2              1

Hopefully that makes the question clearer?

Answer 1

What if you get the count of username and then perform a JOIN with that like

SELECT c.c_name, c.c_groupnumber, count(a.a_userid) AS TotalCount,
xxx.username_count
FROM company c
LEFT JOIN account a ON c.c_groupnumber = a.a_groupnumber
LEFT JOIN ( select u_userid, count(u_username) username_count
            from `user`
            group by u_userid ) xxx ON a.a_userid = xxx.u_userid
WHERE a.a_deleted IS NULL
GROUP BY c.c_groupnumber
HAVING TotalCount > 0;