最近在NodeJS和Postgres中遇到了这个问题。

ES6方法

我知道没有任何RDBMS特性提供这种功能，所以我创建了一个包含我所有字段的对象，例如:

const schema = { columns: ['id','another_column','yet_another_column'] }

定义了一个reducer将字符串与表名连接在一起:

const prefix = (table, columns) => columns.reduce((previous, column) => {
  previous.push(table + '.' + column + ' AS ' + table + '_' + column);
  return previous;
}, []);

这将返回一个字符串数组。为每个表调用它并合并结果:

const columns_joined = [...prefix('tab1',schema.columns), ...prefix('tab2',schema.columns)];

输出最后的SQL语句:

console.log('SELECT ' + columns_joined.join(',') + ' FROM tab1, tab2 WHERE tab1.id = tab2.id');

我可以想到两种方法以可重用的方式实现这一点。一种方法是为所有列重命名，为它们所在的表加上前缀。我已经看过很多次了，但我真的不喜欢。我发现它是多余的，会导致大量的输入，而且当您需要覆盖列名来源不明确的情况时，您总是可以使用别名。

另一种方法是为每个表创建别名表名的视图，这也是我建议您在自己的情况下使用的方法。然后你们就会站在这些观点的对立面，而不是桌子的对立面。这样，如果您愿意，您可以自由地使用*，如果您愿意，可以自由地使用带有原始列名的原始表，而且它还使编写任何后续查询更容易，因为您已经在视图中完成了重命名工作。

最后，我不清楚为什么需要知道每个列来自哪个表。这重要吗?最终重要的是它们所包含的数据。UserID来自User表还是UserQuestion表并不重要。当然，当您需要更新它时，这很重要，但在这一点上，您应该已经足够了解您的模式以确定这一点。

我完全理解为什么这是必要的——至少对我来说，在快速创建原型时，有很多表需要连接，包括许多内部连接，这很方便。只要一个列名在第二个joinedtable中是相同的。*"字段通配符，主表的字段值将被joinedtable值覆盖。容易出错，令人沮丧和违反DRY时，必须手动指定表字段与别名一遍又一遍…

下面是一个PHP (Wordpress)函数，通过代码生成以及如何使用它的示例来实现这一点。在本例中，它用于快速生成一个自定义查询，该查询将提供通过高级自定义fields字段引用的相关wordpress帖子的字段。

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>";
}

输出:

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
        )
)

I see two possible situations here. First, you want to know if there is a SQL standard for this, that you can use in general regardless of the database. No, there is not. Second, you want to know with regard to a specific dbms product. Then you need to identify it. But I imagine the most likely answer is that you'll get back something like "a.id, b.id" since that's how you'd need to identify the columns in your SQL expression. And the easiest way to find out what the default is, is just to submit such a query and see what you get back. If you want to specify what prefix comes before the dot, you can use "SELECT * FROM a AS my_alias", for instance.

不能这样做没有别名，只是因为，你将如何引用一个字段在where子句，如果该字段存在于2或3个表，你要连接? 这将是不清楚的mysql，你试图引用哪一个。

或者你可以使用Red Gate SQL Refactor或SQL Prompt，它通过单击Tab按钮将SELECT *展开为列列表

所以在你的例子中，如果你输入SELECT * FROM A JOIN B… 转到*的末尾，Tab键，瞧!你会看到 选择a . columnn1, A.column2， ....， B. columnn1, B.column2 FROM A JOIN

但它不是免费的