title: SQL Query to sum fields from different tables
body: <p>I'm a humble programmer that hates SQL ... :) Please help me with this query.</p>
  
  <p>I have 4 tables, for example:</p>
  
  <pre><code>Table A:
  Id Total
  1  100
  2  200
  3  500
  
  Table B
  ExtId  Amount
  1      10
  1      20
  1      13
  2      12
  2      43
  3      43
  3      22
  
  Table C
  ExtId  Amount
  1      10
  1      20
  1      13
  2      12
  2      43
  3      43
  3      22
  
  Table D
  ExtId  Amount
  1      10
  1      20
  1      13
  2      12
  2      43
  3      43
  3      22
  </code></pre>
  
  <p>I need to make a SELECT that shows the Id, the Total and the SUM of the Amount fields of tables B, C and D like this</p>
  
  <pre><code>Id Total AmountB AmountC AmountD
  1  100   43      43      43
  2  200   55      55      55
  3  500   65      65      65
  </code></pre>
  
  <p>I've tried with a inner join of the three tables by the Id and doing a sum of the amount fields but results are not rigth. Here is the wrong query:</p>
  
  <pre><code>SELECT     dbo.A.Id, dbo.A.Total, SUM(dbo.B.Amount) AS Expr1, SUM(dbo.C.Amount) AS  Expr2, SUM(dbo.D.Amount) AS Expr3
  FROM         dbo.A INNER JOIN
                    dbo.B ON dbo.A.Id = dbo.B.ExtId INNER JOIN
                    dbo.C ON dbo.A.Id = dbo.C.ExtId INNER JOIN
                    dbo.D ON dbo.A.Id = dbo.D.ExtId
  GROUP BY dbo.A.Id, dbo.A.Total
  </code></pre>
  
  <p>Thanks in advance, its just that I hate SQL (or that SQL hates me).</p>
  
  <p>EDIT: I had a typo. This query is not giving the right results. Extended the example.</p>