来自3个表的SUM表的SQL报告

i have 3 tables see the picture

i want the sql statement which produde report like Required Report in pic.

Select U.UserId, U.Username, D.Dep_Title
    , Coalesce(Sum( Case When T.tr_type = 'Debit' Then -1 Else 1 End * T.Amount )
            ,0) As [Balance (Debit-Credit)]
From Users As U
    Join Department As D
        On D.Dep_Id = U.Dep_Id
    Left Join Transactions As T
        On T.UserId = U.UserId
Group By U.UserId, U.Username, D.Dep_Title

I think the query you are looking for is...

SELECT Userid,
       UserName,
       (SELECT Dep_title
            FROM department
            WHERE USER.dep_id = department.dep_id) AS Dep_title,
       ((SELECT (SUM(amount)
             FROM Transactions
             WHERE Transactions.userid = USER.Userid AND
                   tr_type             = 'Credit') -
        (SELECT (SUM(amount)
             FROM Transactions
             WHERE Transactions.userid = USER.Userid AND
                   tr_type             = 'Debit')) AS "Balance(Debit-Credit)"
    FROM USER;

If I might be permitted a couple of observations; first, your last column title does not appear to reflect the contents of the column, and second, the haphazard capitalisation of your table and column names will lead to a great deal of trouble in the future; I recommend you use a consistent style for capitalisation and abbreviation forming.

It would be easier if amount was negative for debit transactions. Also, the balance is credit - debit, not debit - credit. In any case:

SELECT Userid, UserName, Dep_title,
       ( (SELECT COALESCE(SUM(amount), 0) FROM Transctions WHERE userid = USER.userid AND tr_type = 'Credit')
       - (SELECT COALESCE(SUM(amount), 0) FROM Transctions WHERE userid = USER.userid AND tr_type = 'Debit')
       ) AS Balance
  FROM USER
  JOIN Department USING (dep_id)

this should work (no need for subselects, but this isn't tested):

SELECT
  USER.Userid,
  USER.UserName,
  Department.Dep_title,
  SUM(IF(Transactions.tr_type='Credit',amount,amount*(-1))) as Balance
FROM
  USER,
  Department,
  Transactions
WHERE
  USER.Userid = Transactions.userid
AND
  USER.dep_id = Department.dep_id
GROUP BY
  USER.Userid

You could try something like this:

SELECT
  u.Userid AS Userid,
  u.UserName AS UserName,
  d.Dep_title AS Dep_title,
  SUM(IF(t.tr_type='Credit',-1*t.amount,t.amount)) AS "Balance(Debit-Credit)"
FROM USER AS u
LEFT JOIN Departement AS d USING(dep_id)
LEFT JOIN Transactions AS t ON u.Userid=t.userid
GROUP BY u.Userid

I haven't tested this but you should be able to use the IF statement to work out the difference between credit and debit.

SELECT u.Userid, u.UserName, d.Dep_title, t.Balance
FROM USER As u
    LEFT JOIN Department AS d on u.dep_id = d.dep_id
    LEFT JOIN (SELECT userid, SUM(IF(tr_type = 'Debit', amount, -1*amount)) AS Balance FROM Transactions GROUP BY userid) AS t