Wordpress WP_Query Multiple Queries - mysql

Question

I'm trying to come up with a way of querying a CPT by a specific author but also if a meta_key has a specific value.
For example, my CPT has an author ID attached to it as well as a 'recipient' custom field. What i need is all posts of this type by this author as well as all posts of this type where 'recipient' = this author.
(Hope I've explained that well enough!)
I'm usually pretty OK with SQL but just having a random brain fart moment and can't figure this one out. Like I said, any help is much appreciated!
== Solved ==
Thanks to #3pepe3 for suggesting the meta_query parameter of WP_Query. Modified my CPT logic slightly and now have a beautifully working system.
The solution was to add a new meta field for each post containing the original sender's user id, then run two meta_queries to retrieve posts where the current user_id matches either the sender or recipient fields, likes so:
$args = array(
'post_type' => 'activity',
'post_status' => 'publish',
'orderby' => 'date',
'order' => 'DESC',
'meta_query' => array(
'relation' => 'OR',
array(
'key' => 'sender',
'value' => $user_id,
'type' => 'BINARY',
'compare' => '='
),
array(
'key' => 'recipient',
'value' => $user_id,
'type' => 'BINARY',
'compare' => '='
)
)
);
$query = new WP_Query( $args );

Answer 1

Helo JRM47R1X,
Instead of using SQL queries you should use the WP_Query Class
<?php
$args = array(
'post_type' => 'activity',
'author' => $user_id,
'post_status' => 'publish',
'orderby' => 'date',
'order' => 'DESC',
'meta_query' => array(
array(
'key' => 'recipient',
'value' => $user_id,
'type' => 'BINARY',
'compare' => '='
),
),
);
$query = new WP_Query($args);
?>
The advantage of using the WP_Query is that you can mix meta queries, taxonomies and dates with logical operands like OR, AND BETWEEN....

Answer 2

Ok I eventually figured it out. Turns out all I needed was a Union on the two queries like so:
SELECT * FROM (
SELECT $wpdb->posts.*
FROM $wpdb->posts
WHERE $wpdb->posts.post_author = $user_id
AND $wpdb->posts.post_type = 'activity'
AND $wpdb->posts.post_status = 'publish'
UNION
SELECT $wpdb->posts.*
FROM $wpdb->posts, $wpdb->postmeta
WHERE $wpdb->postmeta.meta_key = 'recipient'
AND $wpdb->postmeta.meta_value = $user_id
AND $wpdb->posts.ID = $wpdb->postmeta.post_id
AND $wpdb->posts.post_type = 'activity'
AND $wpdb->posts.post_status = 'publish'
) as x
ORDER BY x.post_date DESC
Hope this helps anyone else having this bizarrely obscure problem!