title: UNION SQL - Adding a new column to results each time a SELECT statement is called
body: <p>The following code compiles several <code>SELECT</code> statements.</p>
  
  <pre><code>SELECT b.User, SUM(i.ClientFee - i.CentreFee) as '1 Jan - 31 Jan'
  FROM tblInvoices i
  Inner Join tblBooking b
      ON i.B_ID = b.BookingID
  WHERE (i.InvoiceDate BETWEEN '2012-01-01' and '2012-01-31')
  GROUP BY b.User
  
  UNION ALL
  
  SELECT b.User, SUM(i.ClientFee - i.CentreFee) as '1 Feb - 29 Feb'
  FROM tblInvoices i
  Inner Join tblBooking b
      ON i.B_ID = b.BookingID
  WHERE (i.InvoiceDate BETWEEN '2012-02-01' and '2012-02-29')
  GROUP BY b.User
  
  UNION ALL
  
  SELECT b.User, SUM(i.ClientFee - i.CentreFee) as 'Total'
  FROM tblInvoices i
  Inner Join tblBooking b
      ON i.B_ID = b.BookingID
  WHERE (i.InvoiceDate BETWEEN '2012-01-01' and '2012-02-29')
  GROUP BY b.User;
  </code></pre>
  
  <p>Results:</p>
  
  <pre><code>User | 1 Jan - 31 Jan
  ----------------------
  Ben  | 100.00
  Tom  | 210.00
  Fred | 100.00
  Ben  | 250.00
  Tom  | 140.00
  Fred | 150.00
  Ben  | 350.00
  Tom  | 350.00
  Fred | 250.00
  </code></pre>
  
  <p>I am selecting the user (<code>b.User</code>) and their monthly profit (<code>i.clientfee - i.centrfee</code>) from several tables in my company database. For each <code>SELECT</code> statement run I need a new column added to display this statements results. The title of these columns need to be the period start and end dates, please see table below:</p>
  
  <pre><code>User | 1 Jan - 31 Jan | 1 Feb - 29 Feb | Total
  ________________________________________________
  Ben  |-----100.00-----|-----250.00-----| 350.00
  Tom  |-----210.00-----|-----140.00-----| 350.00
  Fred |-----100.00-----|-----150.00-----| 250.00
  </code></pre>
  
  <p>How would I achieve these results?</p>
  
  <p>Any help or suggestions would be appreciated.</p>