Codeigniter：选择所有指定列的前缀字符串

Question

I have the following select queries.

    $this->db->select("$order_table.user_id, $order_table.total_price,
                       $order_table.shipping, $order_table.tax, 
                       $order_table.filled, $order_table.shipped, 
                        $order_table.tracking");
    $this->db->select("$user_table.first_name as user_first_name, 
                       $user_table.last_name as user_last_name, 
                       $user_table.email as user_email");
    $this->db->select("$mailing_address_table.first_name as mailing_first_name, 
                       $mailing_address_table.last_name as mailing_last_name, 
                       $mailing_address_table.address as mailing_address, 
                       $mailing_address_table.address_2 as mailing_address_2, 
                       $mailing_address_table.city as mailing_city, 
                       $mailing_address_table.state as mailing_state, 
                       $mailing_address_table.zip_code as mailing_zip_code, 
                       $mailing_address_table.country as mailing_country");

    $this->db->select("$billing_address_table.first_name as billing_first_name, 
                       $billing_address_table.last_name as billing_last_name, 
                       $billing_address_table.address as billing_address, 
                       $billing_address_table.address_2 as billing_address_2, 
                       $billing_address_table.city as billing_city, 
                       $billing_address_table.state as billing_state,              
                       $billing_address_table.zip_code as billing_zip_code, 
                       $billing_address_table.country as billing_country");

    $this->db->join($user_table, 
                   "$user_table.id = $order_table.user_id", "left");
    $this->db->join($mailing_address_table, 
                   "$mailing_address_table.user_id = $user_table.id", "left");
    $this->db->join($billing_address_table, 
                   "$billing_address_table.user_id = $user_table.id", "left");

Is there anyway, I imagine using CONCAT, that I can prefix "billing_" to each column that I'm selecting in billing. I can't seem to figure this out when I'm not selecting everything, but rather just specific columns.

Id like each column I select from $user_table to be prefix with "user_", $mailing_table "mailing_" and so on.

Note:

1) I am not selecting all the fields from each column in these select queries, so I can't do SELECT * FROM...

2) I don't want to UPDATE the column names in the database, just for this specific SELECT use.

Answer 1

Here you can create to field list:

SET @SCHEMA = 'toimport';

SET @PREFIX = 'billing_';
SET @POSTFIX = 'address';

SELECT GROUP_CONCAT(
 CONCAT(@SCHEMA,'.',@PREFIX,'.',@POSTFIX,'.',COLUMN_NAME,
 ' AS ',@PREFIX,COLUMN_NAME) SEPARATOR ',
')
 FROM information_schema.COLUMNS
 WHERE TABLE_SCHEMA = @SCHEMA AND TABLE_NAME = CONCAT( @PREFIX,  @POSTFIX );

The Result look likes:

toimport.billing_.address.id AS billing_id,
toimport.billing_.address.name AS billing_name,
toimport.billing_.address.street AS billing_street,
toimport.billing_.address.a1 AS billing_a1,
toimport.billing_.address.a2 AS billing_a2