これが必要な理由は完全に理解できます。少なくとも、多くの内部結合を含め、結合する必要のあるテーブルがたくさんある場合、ラピッドプロトタイピングの際に便利です。2番目の「joinedtable。*」フィールドのワイルドカードで列名が同じになるとすぐに、メインテーブルのフィールド値がjointabletableの値で上書きされます。エイリアスを使用してテーブルフィールドを何度も手動で指定する必要がある場合、エラーが発生しやすく、イライラし、DRYに違反します...
これは、コード生成を通じてこれを実現するためのPHP(Wordpress)関数と、その使用方法の例です。この例では、高度なカスタムフィールドフィールドを通じて参照された関連ワードプレス投稿のフィールドを提供するカスタムクエリを迅速に生成するために使用されます。
function prefixed_table_fields_wildcard($table, $alias)
{
global $wpdb;
$columns = $wpdb->get_results("SHOW COLUMNS FROM $table", ARRAY_A);
$field_names = array();
foreach ($columns as $column)
{
$field_names[] = $column["Field"];
}
$prefixed = array();
foreach ($field_names as $field_name)
{
$prefixed[] = "`{$alias}`.`{$field_name}` AS `{$alias}.{$field_name}`";
}
return implode(", ", $prefixed);
}
function test_prefixed_table_fields_wildcard()
{
global $wpdb;
$query = "
SELECT
" . prefixed_table_fields_wildcard($wpdb->posts, 'campaigns') . ",
" . prefixed_table_fields_wildcard($wpdb->posts, 'venues') . "
FROM $wpdb->posts AS campaigns
LEFT JOIN $wpdb->postmeta meta1 ON (meta1.meta_key = 'venue' AND campaigns.ID = meta1.post_id)
LEFT JOIN $wpdb->posts venues ON (venues.post_status = 'publish' AND venues.post_type = 'venue' AND venues.ID = meta1.meta_value)
WHERE 1
AND campaigns.post_status = 'publish'
AND campaigns.post_type = 'campaign'
LIMIT 1
";
echo "<pre>$query</pre>";
$posts = $wpdb->get_results($query, OBJECT);
echo "<pre>";
print_r($posts);
echo "</pre>";
}
出力:
SELECT
`campaigns`.`ID` AS `campaigns.ID`, `campaigns`.`post_author` AS `campaigns.post_author`, `campaigns`.`post_date` AS `campaigns.post_date`, `campaigns`.`post_date_gmt` AS `campaigns.post_date_gmt`, `campaigns`.`post_content` AS `campaigns.post_content`, `campaigns`.`post_title` AS `campaigns.post_title`, `campaigns`.`post_excerpt` AS `campaigns.post_excerpt`, `campaigns`.`post_status` AS `campaigns.post_status`, `campaigns`.`comment_status` AS `campaigns.comment_status`, `campaigns`.`ping_status` AS `campaigns.ping_status`, `campaigns`.`post_password` AS `campaigns.post_password`, `campaigns`.`post_name` AS `campaigns.post_name`, `campaigns`.`to_ping` AS `campaigns.to_ping`, `campaigns`.`pinged` AS `campaigns.pinged`, `campaigns`.`post_modified` AS `campaigns.post_modified`, `campaigns`.`post_modified_gmt` AS `campaigns.post_modified_gmt`, `campaigns`.`post_content_filtered` AS `campaigns.post_content_filtered`, `campaigns`.`post_parent` AS `campaigns.post_parent`, `campaigns`.`guid` AS `campaigns.guid`, `campaigns`.`menu_order` AS `campaigns.menu_order`, `campaigns`.`post_type` AS `campaigns.post_type`, `campaigns`.`post_mime_type` AS `campaigns.post_mime_type`, `campaigns`.`comment_count` AS `campaigns.comment_count`,
`venues`.`ID` AS `venues.ID`, `venues`.`post_author` AS `venues.post_author`, `venues`.`post_date` AS `venues.post_date`, `venues`.`post_date_gmt` AS `venues.post_date_gmt`, `venues`.`post_content` AS `venues.post_content`, `venues`.`post_title` AS `venues.post_title`, `venues`.`post_excerpt` AS `venues.post_excerpt`, `venues`.`post_status` AS `venues.post_status`, `venues`.`comment_status` AS `venues.comment_status`, `venues`.`ping_status` AS `venues.ping_status`, `venues`.`post_password` AS `venues.post_password`, `venues`.`post_name` AS `venues.post_name`, `venues`.`to_ping` AS `venues.to_ping`, `venues`.`pinged` AS `venues.pinged`, `venues`.`post_modified` AS `venues.post_modified`, `venues`.`post_modified_gmt` AS `venues.post_modified_gmt`, `venues`.`post_content_filtered` AS `venues.post_content_filtered`, `venues`.`post_parent` AS `venues.post_parent`, `venues`.`guid` AS `venues.guid`, `venues`.`menu_order` AS `venues.menu_order`, `venues`.`post_type` AS `venues.post_type`, `venues`.`post_mime_type` AS `venues.post_mime_type`, `venues`.`comment_count` AS `venues.comment_count`
FROM wp_posts AS campaigns
LEFT JOIN wp_postmeta meta1 ON (meta1.meta_key = 'venue' AND campaigns.ID = meta1.post_id)
LEFT JOIN wp_posts venues ON (venues.post_status = 'publish' AND venues.post_type = 'venue' AND venues.ID = meta1.meta_value)
WHERE 1
AND campaigns.post_status = 'publish'
AND campaigns.post_type = 'campaign'
LIMIT 1
Array
(
[0] => stdClass Object
(
[campaigns.ID] => 33
[campaigns.post_author] => 2
[campaigns.post_date] => 2012-01-16 19:19:10
[campaigns.post_date_gmt] => 2012-01-16 19:19:10
[campaigns.post_content] => Lorem ipsum
[campaigns.post_title] => Lorem ipsum
[campaigns.post_excerpt] =>
[campaigns.post_status] => publish
[campaigns.comment_status] => closed
[campaigns.ping_status] => closed
[campaigns.post_password] =>
[campaigns.post_name] => lorem-ipsum
[campaigns.to_ping] =>
[campaigns.pinged] =>
[campaigns.post_modified] => 2012-01-16 21:01:55
[campaigns.post_modified_gmt] => 2012-01-16 21:01:55
[campaigns.post_content_filtered] =>
[campaigns.post_parent] => 0
[campaigns.guid] => http://example.com/?p=33
[campaigns.menu_order] => 0
[campaigns.post_type] => campaign
[campaigns.post_mime_type] =>
[campaigns.comment_count] => 0
[venues.ID] => 84
[venues.post_author] => 2
[venues.post_date] => 2012-01-16 20:12:05
[venues.post_date_gmt] => 2012-01-16 20:12:05
[venues.post_content] => Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
[venues.post_title] => Lorem ipsum venue
[venues.post_excerpt] =>
[venues.post_status] => publish
[venues.comment_status] => closed
[venues.ping_status] => closed
[venues.post_password] =>
[venues.post_name] => lorem-ipsum-venue
[venues.to_ping] =>
[venues.pinged] =>
[venues.post_modified] => 2012-01-16 20:53:37
[venues.post_modified_gmt] => 2012-01-16 20:53:37
[venues.post_content_filtered] =>
[venues.post_parent] => 0
[venues.guid] => http://example.com/?p=84
[venues.menu_order] => 0
[venues.post_type] => venue
[venues.post_mime_type] =>
[venues.comment_count] => 0
)
)