How to create tree based query from same table in mysql? - php

Question

Hey guys i want to create one tree based data in my html view from mysql.
I have one table salary_slip there 2 columns pay_month and pay_year.
data is like this:
pay_month pay_year
February 2014
march 2014
January 2015
February 2015
April 2015
may 2015
June 2015
January 2016
march 2016
December 2016
So now i want to create tree view for the same.so, if user will click on 2016(pay_year) onclick this all data in pay_month in front of 2016 should be display in tree format and same for the all.
My current query is:
select
PAY_MONTH,
PAY_YEAR
from
india_salary_slip_details
where
EMPLOYEE_ID = 34
group by
pay_year
By this i got my data:
but i can only see each year's first month only.
please provide me with better query so i can get my result.
image for the same:current data from my query

Answer 1

A major part of your problem comes from the use of GROUP BY, which is used for, well, grouping.
MySQL has different handling of GROUP BY than other DBMS' that require all non-aggregate fields to be listed in the GROUP BY clause. MySQL give you enough rope with which to hang yourself (so to speak), which is why you didn't get an error for what is clearly not an intended use of GROUP BY.
Depending on how your front end is handling the data, you have a few options.
Option 1) Have it load (ordered) and use the output loop to determine the change in year.
SQL Query:
SELECT
PAY_MONTH,
PAY_YEAR
FROM
india_salary_slip_details
WHERE
EMPLOYEE_ID = 34
ORDER BY
pay_year,
pay_month -- we want it ordered by year, then month, though this will be alphabetical due to the data type
PHP Code:
<?php
$year = NULL;
foreach ($result as $row) { // Assuming your result is stored as $result
if ($row['PAY_YEAR'] !== $year) {
// Print the year in the left column so to speak, perhaps create a sublist, etc
// Set the year
$year = $row['PAY_YEAR'];
}
// Add month
// Do something with $row['PAY_MONTH'], perhaps add it to a sublist, again, depends on front end handling.
}
Option 2) Have it load the years, then the next level asynchronously.
SQL Query to get years:
SELECT DISTINCT
PAY_YEAR
FROM
india_salary_slip_details
WHERE
EMPLOYEE_ID = 34
ORDER BY
PAY_YEAR
SQL Query to get months given a year:
SELECT
PAY_MONTH
FROM
india_salary_slip_details
WHERE
EMPLOYEE_ID = 34
AND PAY_YEAR = (Whatever the year is)
ORDER BY
PAY_MONTH

Answer 2

The problem is your group by, you just want to order by year :
SELECT PAY_MONTH, PAY_YEAR, FROM india_salary_slip_details WHERE EMPLOYEE_ID = 34
ORDER BY PAY_YEAR