Select where class from wordpress database: - php

Question

I need help to this select where class from wordpress database:
What I would like to achieve is to display the first 6 newcomer posts/records.
The path to the image, image name, property title, property features (How many Bedrooms and Bathroom etc. there is)
property price and property price unit (if it $ or Danish kroner etc.)
At this link All properties here you can see what i will like to achieve on my front page, just without google map and the sort list and only the 6 first post:
All properties
This are tables: wp_wpl_properties, wp_wpl_units, wp_wpl_items to achieve my goal so i tried to make this select query:
enter code here
<?php
global $wpdb;
$results = $wpdb->get_results
("SELECT * FROM wp_wpl_properties,wp_wpl_units,wp_wpl_items
where wp_wpl_properties.price_unit= wp_wpl_units.id and wp_wpl_properties.id= wp_wpl_items.parent_id LIMIT 6;");
foreach ( $results as $result ) {
?>
I have attached table files to this question, here:
wp_wpl_units.pdf
wp_wpl_items.pdf
wp_wpl_properties (1).sql
The code I've made does not make any errors.
My problem is that i get the same record displayed 3 times at the fist columns and the same at the next 3 column, hope this make sens :)
Here is a link to my frontpage: My frontpage

Answer 1

Do you want like this?
$results = $wpdb->get_results ("
SELECT * FROM wp_wpl_properties
join wp_wpl_units on wp_wpl_properties.living_area_unit= wp_wpl_units.id
join wp_wpl_properties on wp_wpl_properties.id= wp_wpl_items.parent_id LIMIT 6");
or
$results = $wpdb->get_results ("
SELECT * FROM wp_wpl_properties
join wp_wpl_units on wp_wpl_properties.living_area_unit= wp_wpl_units.id
join wp_wpl_properties on wp_wpl_properties.id= wp_wpl_items.parent_id
where wp_wpl_properties.id= 1");

Answer 2

$results = $wpdb->get_results
("SELECT * FROM wp_wpl_properties
Inner Join wp_wpl_units ON wp_wpl_properties.living_area_unit = wp_wpl_units.id
Inner Join wp_wpl_items ON wp_wpl_properties.id= wp_wpl_items.parent_id
LIMIT 6;");

Answer 3

In your MySQL query,
SELECT * FROM wp_wpl_properties,
wp_wpl_units,
wp_wpl_items
where wp_wpl_properties.price_unit=wp_wpl_units.id
and wp_wpl_properties.id= wp_wpl_items.parent_id
LIMIT 6
MySQL individually checks each of the three columns differently and generates output for all of them even though they are same.
Doing an inner join instead of checking individually on three columns would be the solution. Like,
SELECT DISTINCT * FROM wp_wpl_properties as props
Inner Join wp_wpl_items as items ON items.parent_id = props.id
Inner Join wp_wpl_units as units ON units.id = props.living_area_unit
LIMIT 6
And instead of select distinct * from, get only the columns you need. it will speed up the query to a large extent!
like SELECT DISTINCT props.ID, items.ID FROM ....
Hope this helps.