sum of values based on condition - mysql

Question

Iam new to mysql
I have two tables,
CREATE TABLE `tab1` (
`tid1` int(2) NOT NULL auto_increment,
`payer` varchar(100) default NULL,
`receiver` varchar(100) default NULL,
`payAmt` decimal(20,2) default '0.00',
`recAmt` decimal(20,2) default '0.00',
PRIMARY KEY (`tid1`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ;
--
-- Dumping data for table tab1
INSERT INTO `tab1` (`tid1`, `payer`, `receiver`, `payAmt`, `recAmt`) VALUES
(1, 'aaa', 'bbb', 100.00, -100.00),
(2, 'aaa', 'ccc', 200.00, -200.00),
(3, 'bbb', 'aaa', 150.00, -150.00),
(4, 'ccc', 'aaa', 175.00, -175.00);
--
-- Table structure for table tab2
CREATE TABLE `tab2` (
`tid2` int(2) NOT NULL auto_increment,
`payer` varchar(100) default NULL,
`receiver` varchar(100) default NULL,
`payAmt` decimal(20,2) default '0.00',
`recAmt` decimal(20,2) default '0.00',
PRIMARY KEY (`tid2`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;
--
-- Dumping data for table tab2
INSERT INTO `tab2` (`tid2`, `payer`, `receiver`, `payAmt`, `recAmt`) VALUES
(1, 'ddd', 'aaa', 223.00, -223.00),
(2, 'aaa', 'bbb', 429.00, -429.00),
(3, 'ccc', 'aaa', 102.00, -102.00);
I want the result as shown below
name payAmtTotal recAmtTotal payAmtTotal-recAmtTotal
aaa 729 650 79
bbb 150 529 -379
ccc 277 -277 554
ddd 223 0 223

Answer 1

Not sure why there is more then 1 table with this information, first thing that comes up is trying to turn this into 1 table.
Anyway, not sure if this is the best and cleanest way bu if the tables aren't to large and you have to option of creating temporary tables then here's one way of getting the desired results.
CREATE TEMPORARY TABLE IF NOT EXISTS temp1 AS (SELECT * FROM `tab1`);
INSERT INTO temp1 SELECT * FROM `tab2`;
CREATE TEMPORARY TABLE IF NOT EXISTS temp2 AS (SELECT * FROM `temp1`);
CREATE TEMPORARY TABLE IF NOT EXISTS temp3 AS (SELECT * FROM `temp1`);
SELECT
`payer` AS `name`,
(SELECT SUM(payAmt) AS `p` FROM temp2 AS t WHERE t.payer = temp1.payer) AS `payAmtTotal` ,
(SELECT SUM(payAmt) AS `r` FROM temp3 AS t WHERE t.receiver = temp1.payer) AS `recAmtTotal`
FROM
temp1
GROUP BY `name`;
Basically you create a singe (temporary) table and fill this table with the data from the two existing tables.
Since MySQL won't let you use the same temporary table more then once in a single query you need to create a few more :-) they can be copies of the first one though.
After that the selection query on itself isn't that complicated.