how to combine more than one mysql query into single query - php

Question

i have 3 different queries like below:
$query = "select category_id,category_name from category";
$result = $this->Dbmodel->customQueryResult($query);
$query = "select location,location_name from sub_category";
$result_one = $this->Dbmodel->customQueryResult($query);
$query = "select category_date,category_month from other_category";
$result_two = $this->Dbmodel->customQueryResult($query);
here i am calling mysql server 3 times to execute my query and getting the result thereby..
now i am thinking how can i reduce mysql call so that all these 3 query gets executed in one single query so making only 1 call to mysql server and displaying all different results to user using php
how can i do this.. any help or suggestion would be a great help.. thanks in advance

Answer 1

What you've described is an SQL UNION.
Below is an example query you could use to achieve your goal:
SELECT category_id,category_name FROM category
UNION
SELECT location,location_name FROM sub_category
UNION
SELECT category_date,category_month FROM other_category
Example usage:
$query = 'SELECT category_id, category_name FROM category
UNION
SELECT location, location_name FROM sub_category
UNION
SELECT category_date, category_month FROM other_category';
$result = $this->Dbmodel->customQueryResult($query);
echo 'CategoryID: ' . $result['category_id'] . '<br />';
echo 'Category Name: ' . $result['category_name'] . '<br />';
echo 'Location: ' . $result['location'] . '<br />';
echo 'Location Name: ' . $result['location_name'] . '<br />';
echo 'Category Date: ' . $result['category_date'] . '<br />';
echo 'Category Month: ' . $result['category_month'];
Keep in mind, in case you need to select fields with identical names from different tables to use SQL aliases. An example of an alias:
SELECT category_id AS `catID` FROM category
Instead of $result['category_id'], you would use $result['catID'] instead.

Answer 2

As you are saying none of the tables are related, you have to fetch 3 queries.
You shouldn't combine queries, if there is no any relation. Otherwise it will give you ambiguous data.
We use sub-queries, joins when there is some relation to minimize queries.
Anyways you can get 3 queries result, if 1st, 2nd column have same data type and you can identify from 3rd column it's table name.
SELECT category_id,category_name, 'category' FROM category
UNION
SELECT location,location_name, 'sub_category' FROM sub_category
UNION
SELECT category_date,category_month, 'other_category' FROM other_category

Answer 3

THIS WILL BE EXACT QUERY
$query = "select category.category_id,category.category_name, sub_category.location,sub_category.location_name,other_category.category_date,other_category.category_month from category,sub_category,other_category";
You can use joint properties something like that.
$query = "select * from category, sub_category, other_category";
Note: on *, you can read this question MySQL - specific columns on join?

Answer 4

If the tables are related you could use joins. If that not the case you could use mysql UNION
It would be something like ...
$query = "select category_id,category_name from category UNION select location,location_name from sub_category UNION select category_date,category_month from other_category";

Answer 5

If all 3 Query have same data then we can Combine all 3 queries, Otherwise it would be not useful.
The Other way, Would be as Follows
Select c.category_id, c.category_name,
l.location,l.location_name,
o.category_date,o.category_month
from category C,
sub_category l,
other_category o
But Above would does get the Meaningful Data.