とりあえず以下の記述で取得できたのでメモしておきます。
post_type01→一つ目のポストタイプ
post_type02→二つ目のポストタイプ
meta_key1→二つ目のポストタイプのカスタムフィールドのキー1
meta_key2→二つ目のポストタイプのカスタムフィールドのキー2
global $wpdb; //SQLに挿入する変数 $search_key_leases = array('value1','value2','value3', $min_price, $max_price); $sql = $wpdb->prepare(" SELECT ID as lease_id, lm1.meta_value AS value1 , lm2.meta_value AS value2 , lm3.meta_value AS value3 FROM $wpdb->posts LEFT JOIN $wpdb->postmeta AS lm1 ON (ID = lm1.post_id AND lm1.meta_key = %s) LEFT JOIN $wpdb->postmeta AS lm2 ON (ID = lm2.post_id AND lm2.meta_key = %s) LEFT JOIN $wpdb->postmeta AS lm3 ON (ID = lm3.post_id AND lm3.meta_key = %s) WHERE post_type = 'post_type01' AND post_status = 'publish' AND lm3.meta_value IS NULL AND lm2.meta_value <= CURDATE() AND lm1.meta_value IN (SELECT ID FROM $wpdb->posts LEFT JOIN $wpdb->postmeta AS pm1 ON (ID = pm1.post_id AND pm1.meta_key = 'meta_key1') LEFT JOIN $wpdb->postmeta AS pm2 ON (ID = pm2.post_id AND pm2.meta_key = 'meta_key2') WHERE post_type = 'post_type02' AND post_status = 'publish' AND pm1.meta_value = '合致させたい内容' AND pm2.meta_value BETWEEN %d AND %d )", $search_key_leases); $results = $wpdb->get_results($sql, ARRAY_A); if($results) { foreach ($results as $result) { $value_ids[] = $result['value1']; } }