MySQL Get AVR and save in New field - php

Question

Hello I have this problem and can't find a solution:
I have 4 tables with same structure for example as follows:
Table 1: Result
Table 2: Store 1
Table 3: Store 2
Table 4: Store 3
Tables fields: ID - Code - Name - Value
I need a query to read the "Value" for each specific record from tables (Store 1 - Store 2 - Store 3) and calculate the average and save it in table (Result)...
and go on for the next record until it's done.
Note: I'm using PHP and MySQL...
Thanks in advanced...
SELECT
result.id,
result.`code`,
result.`name`,
result.value,
term1.value,
term2.value,
term3.value
FROM result
INNER JOIN store1 ON result.`code` = store1.`code`
INNER JOIN store2 ON result.`code` = store2.`code`
INNER JOIN store3 ON result.`code` = store3.`code`
WHERE result.`code` = 123456
ORDER BY result.serial ASC

Answer 1

The average is just the sum of the values divided by the number of values (3), this is grade school arithmetic.
UPDATE result AS r
JOIN store1 AS s1 ON s1.code = r.code
JOIN store2 AS s2 ON s2.code = r.code
JOIN store3 AS s3 ON s3.code = r.code
SET r.value = (s1.value+s2.value+s3.value)/3
To do lots of columns, you can generate the SQL in PHP:
$cols = array('col1', 'col2', 'col3', ...);
$sets = implode(', ', array_map(function($col) {
return "r.$col = (s1.$col + s2.$col + s3.$col)/3";
}, $cols));
$sql = "UPDATE result AS r
JOIN store1 AS s1 ON s1.code = r.code
JOIN store2 AS s2 ON s2.code = r.code
JOIN store3 AS s3 ON s3.code = r.code
SET $sets";
If you're using PHP before 5.3.0, you can define a named function to call it with array_map
function make_assignment($col) {
return "r.$col = (s1.$col + s2.$col + s3.$col)/3";
}
$sets = implode(', ', array_map('make_assignment', $cols));

Answer 2

You can create views in MySQL for this. Then there will not need any for this. View is a virtual table. On every change in any table it will automatically updated. You don't need any query
create view result as select t1.code as code,(t1.value+t2.value+t3.value)/3 as value from `testcake`.`test1` as t1 JOIN `testcake`.`test2` as t2 ON t1.code = t2.code JOIN `testcake`.`test3` as t3 ON t1.code = t3.code