Querying Email Addresses for a List of Users with Same Last Name?

The question:

I have a site with many users and many of them have the same last name. I want to get the emails of all the users with the same last name (IE: Smith) that has a post related to a particular taxonomy term (IE: Baseball).

So far I have this code that works great in getting all the users with the same last name ( thanks to Mike Schinkel ). I suck at using the JOIN function but I am learning and I really need this sooner than later, so I need help.

$sql =<<<SQL
SELECT
  {$wpdb->users}.user_email,
  {$wpdb->usermeta}.meta_value
FROM
  {$wpdb->users}
  LEFT JOIN {$wpdb->usermeta} ON {$wpdb->users}.ID = {$wpdb->usermeta}.user_id
WHERE 1=1
  AND {$wpdb->users}.user_status = '0'
  AND {$wpdb->usermeta}.meta_key = 'last_name'
  AND {$wpdb->usermeta}.meta_value = 'Smith'
SQL;
  $usersemails = $wpdb->get_results($sql);
  header('Content-type:text/plain');
  print_r($usersemails); 

Your time is greatly appreciated and I will pay it forward. Thanks.

The Solutions:

Below are the methods you can try. The first solution is probably the best. Try others if the first one doesn’t work. Senior developers aren’t just copying/pasting – they read the methods carefully & apply them wisely to each case.

Method 1

Hi @Holidaymaine:

Here’s the query you are looking for:

<?php

include( '../wp-load.php' );

$sql =<<<SQL
SELECT DISTINCT
  u.user_email AS user_email,
  um.meta_value AS user_lastname
FROM
  {$wpdb->users} AS u
  LEFT JOIN {$wpdb->usermeta} AS um ON u.ID = um.user_id
  LEFT JOIN {$wpdb->posts} AS p ON u.ID = p.post_author
  LEFT JOIN {$wpdb->term_relationships} AS tr ON p.ID = tr.object_id
  LEFT JOIN {$wpdb->term_taxonomy} AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
  LEFT JOIN {$wpdb->terms} AS t ON tt.term_id = t.term_id
WHERE 1=1
  AND u.user_status = '0'
  AND um.meta_key = 'last_name'
  AND um.meta_value = '%s'
  AND t.slug = '%s'
SQL;
  $sql = $wpdb->prepare( $sql, 'Smith', 'baseball' );
  $usersemails = $wpdb->get_results( $sql );
  header( 'Content-type:text/plain' );
  print_r( $usersemails );


All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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