Question

id  mem_id   tran_date  tran_type   tran_points plus_minus
-----------------------------------------------------------
 1    2     2011-10-19    test           50         +
 2    2     2011-10-19    test           50         +  
 3    3     2011-10-19    test           50         +
 4    2     2011-10-19    test           15         -

For every individual member all the values in tran_points needs to be added when data in plus_minus column = ‘+’ and the sum of value in tran_points needs to be substracted when data in plus_minus = ‘-‘

I want to have the following output :

member_id   points_balance
--------------------------
   2            85
   3            50

Answer 1

For the table below:

CREATE TABLE t_test
 (a INTEGER,
  b INTEGER,
  c VARCHAR(1)
 );

and for the entries below:

INSERT INTO t_test values(1,50,'+');
INSERT INTO t_test values(1,30,'+');
INSERT INTO t_test values(1,15,'-');
INSERT INTO t_test values(2,30,'+');
INSERT INTO t_test values(2,40,'+');

This query works as you expected:

SELECT a,SUM((CONCAT(c,b)) +0) as t FROM t_test group by a;

a   t
1   65
2   70