Question

Hi i have to write a mysql query i will explain the query how i want to work.

I have two table

A

CREATE TABLE IF NOT EXISTS `A` (
  `field1` int(10) NOT NULL AUTO_INCREMENT,
  `field2` int(10) NOT NULL,
  `field3` int(10) NOT NULL,
  `field4` varchar(255) DEFAULT NULL,
  `fields5` int(10) NOT NULL,
  `field6` varchar(255) NOT NULL,
  `field7` varchar(255) NOT NULL,
  `field8` int(10) NOT NULL,
  `field9` tinyint(1) NOT NULL COMMENT '1=for enabled resource 0= for
disabled resource',
  PRIMARY KEY (`field1`);

table B

CREATE TABLE IF NOT EXISTS `estimate_resource_mth` (
  `field1` int(10) NOT NULL AUTO_INCREMENT,
  `field2` int(10) NOT NULL,
  `field3` int(10) NOT NULL,
  `field4` int(10) NOT NULL,
  PRIMARY KEY (`field1`) ;

There is one to many reference from tableA to tableB that is A.field1 multiple reference to B.table2. Now i will explain what i need to get, i have an id which fetch the data from table A using where condition i need to return this list with the sum of filed4 in tableB(field2 in tableB reference to tableA and it may be a multple row one to many relatio ). How could i got a this data in a single query.

Answer 1

Your description is poor and your generic column names are not very helpful, but if I understand, tableB.field2 references tableA.field1. In that case, a LEFT JOIN with an aggregate SUM() on tableB.field4 will do the job.

SELECT
  tableA.field1,
  SUM(tableB.field4) AS the_sum
FROM
  tableA 
  LEFT JOIN tableB ON tableA.field1 = tableB.field2
WHERE
  /* IN() for multiple possible vals. Use = if only 1 val needed
     and then the GROUP BY is unnecessary */
  tableA.field1 IN ('val1','val2',val3')
GROUP BY tableA.field1