select to multiply tables for print mysqli_num_rows - php

Question

Good evening all.
Is there one that will give me an example of how to make such a script here:
I try to make a while combining 2 different tables in my database to get correct mysqli_num_rows.
Like this:
$Querypris ("SELECT * FROM" wpd2_posts` where post_status = 'wc-failed' and select * From `wpd2_postmeta` where meta_key = '_ order_total' and meta_value> 300 ')
$Num_rowspris = mysqli_num_rows ($ query price);
So I want to get mysqli_num_rows from all those who are post_status = 'wc-completed' but also meta_value> 300
Hope you understand what I mean :)

Answer 1

Well, your php code will not work like this. At least variable names must be consistent.
You should use JOIN clause in your sql statement. I suppose, there is a column like "post_id" in both tables.
$query_price = "SELECT * FROM wpd2_posts JOIN wpd2_postmeta USING (post_id) WHERE post_status = 'wc-completed' AND meta_key = '_order_total' AND meta_value > 300";
$result = mysqli_query($connection, $query_price);
$number_of_rows = mysqli_num_rows($result);
UPDATE:
If names of the columns, referring to ID of the post, are different in those tables, for example "ID" in "wpd2_posts" and "post_id" in "wpd2_postmeta", then you should use a following query:
SELECT * FROM wpd2_posts p JOIN wpd2_postmeta pm
ON p.ID = pm.post_id
WHERE p.post_status = 'wc-completed'
AND pm.meta_key = '_order_total' AND pm.meta_value > 300
UPDATE: removed space from '_ order_total'. changed to '_order_total'

Answer 2

SELECT * FROM wpd2_posts,wpd2_postmeta where wpd2_posts.post_status = wc-completed and wpd2_postmeta.meta_key = _ order_total and wpd2_postmeta.meta_value > 300 and wpd2_posts.fk=wpd2_postmeta.fk
this thing might not work for not having foreign key
SELECT * FROM wpd2_posts CROSS JOIN wpd2_postmeta where wpd2_posts.post_status = wc-completed and wpd2_postmeta.meta_key = _ order_total and wpd2_postmeta.meta_value > 300
Its better to use foreign keys.
hope this will help

Answer 3

If your site is WordPress then use this:
global $wpdb;
$sql="SELECT * FROM wpd2_posts pt INNER JOIN wpd2_postmeta pmt ON pmt.post_id = pt.ID WHERE pt.post_status = 'wc-completed' AND pmt.meta_key = '_order_total' AND pmt.meta_value>300";
$results = $wpdb->get_results($sql, ARRAY_A );
$num_rowspris = count($results);
// OR ---------
$results = $wpdb->query($sql);
$num_rowspris = $results->num_rows;
else :
Note: $conn is your DB connection
$results = mysqli_query($conn, $sql);
$num_rowspris = mysqli_num_rows($results);