complex MySQL query wrong results

Question

I am trying to build complex mysql query but its returning wrong results...

SELECT
  b.name  AS batch_name,
  b.id    AS batch_id,

  COUNT(DISTINCT s.id)
           


        

Answer 1

You still haven't provided full information - no batches table, even the not existing recipts table.. Anyway, I assume we don't care whats in the batches table, lets say it's just the name and id. Your receipts table have multiple rows for the same student. This should result in multiple rows returned for the other tables as well, due to all the JOINs. Therefore you SUM() multiple times values which must be summed just once, i.e. open_balance. This could be a clue as to where the problem is, I'd say you have to move the info that you need from 'the receipts table into subqueries, but I'm not sure you've shown us the entirety of your DB. Try removing the receipts table from the query and check the results again. If that's it, you should see what to do from there on or at least give more info to us.

EDIT: The query should be:

SELECT
  b.name  AS batch_name,
  b.id    AS batch_id,

  COUNT(DISTINCT s.id)
    AS total_students,

  COALESCE( SUM(s.open_bal), 0 )
    AS open_balance,

  SUM(  COALESCE(i.reg_fee,   0)
      + COALESCE(i.tut_fee,   0)
      + COALESCE(i.other_fee, 0)
  ) AS gross_fee,

  SUM( COALESCE(i.discount, 0) )
    AS discount,

  COALESCE( SUM(s.open_bal), 0 )
    + SUM(  COALESCE(i.reg_fee,   0)
          + COALESCE(i.tut_fee,   0)
          + COALESCE(i.other_fee, 0)
      )
    - SUM( COALESCE(i.discount, 0) )
    AS net_payable,
  SUM((SELECT SUM(COALESCE(receipts.reg_fee,   0)
      + COALESCE(receipts.tut_fee,   0)
      + COALESCE(receipts.other_fee, 0)) FROM receipts WHERE receipts.student_id = s.id))
  AS net_recieved,

  ( COALESCE( SUM(s.open_bal), 0 )
    + SUM(  COALESCE(i.reg_fee,   0)
          + COALESCE(i.tut_fee,   0)
          + COALESCE(i.other_fee, 0)
      )
    - SUM(  COALESCE(i.discount,  0) )
  ) 
  - SUM((SELECT SUM(COALESCE(receipts.reg_fee,   0)
          + COALESCE(receipts.tut_fee,   0)
          + COALESCE(receipts.other_fee, 0)) FROM receipts WHERE receipts.student_id = s.id)) 
    AS balance_due

  FROM batches b
  LEFT JOIN students s ON s.batch      = b.id
  LEFT JOIN invoices i ON i.student_id = s.id
  WHERE s.inactive = 0
  GROUP BY b.name, b.id;

This will sum students data in the receipts table even if it's on more than one row, returning just one row. Removing the join to the receipts table removes duplicate lines from the other tables, so the calculations should now be correct.

One more thing - you've got s.inactive = 0 in the WHERE clause, make sure it's not relevant to this calculations.

P.S. How come you don't know what a sub query is and you end up writing stuff like that?