问题
Using Datamapper 1.8.1-dev for PHP's CodeIgniter, I'm trying to build this query to prioritize one country name at top of the list:
SELECT * FROM countries
ORDER BY CASE name WHEN 'Australia' THEN 1 ELSE 2 END, name
PHP on my Country model (which extends Datamapper):
$countries = new Country();
$countries->order_by("CASE name WHEN 'Australia' THEN 1 ELSE 2 END, name");
$countries->get_iterated();
Datamapper instead parses "CASE" as a table name, building this syntax error query:
SELECT * FROM (`countries`)
ORDER BY `CASE` name WHEN 'Australia' THEN 1 ELSE 2 END, `countries`.`name`
I'm assuming the CASE case isn't being handled since this flow control statement was just added in MySQL 5? Are my only alternatives to either add an order_by
column to the countries
table or use a PHP sort function after database retrieval?
回答1:
Datamapper’s order_by()
is just an alias for $this->db->order_by()
.
Unfortunately, as per CodeIgniter Documentation, the Database classes are the only ones that are non-extendable. You're going to have to get your hands dirty by modifying the core.
Head into system/database/DB_active_rec.php
and search for the order_by()
function. Add a third parameter to the function's function definition:
function order_by($orderby, $direction = '', $case = null)
Scroll to the bottom of the function... Just before assigning the $orderby_statement
to $this->ar_orderby[]
write:
if($case===true) $orderby_statement = "CASE " . $orderby_statement;
Save the file and head into application/libraries/datamapper.php
and search for the order_by()
function. Notice, it's just a wrapper!
Replace it with:
public function order_by($orderby, $direction = '', $case = null)
{
$this->db->order_by($this->add_table_name($orderby), $direction, $case);
//For method chaining
return $this;
}
Now, in your controller, if you pass true
as the third parameter to order_by()
, and drop the CASE keyword from the first string param, you should get the correct syntax.
Hope this helps.
回答2:
I was able to use a case statement in an order by. You just need to wrap the case statement in parentheses. If you don't the word case is treated as a column name and back quoted.
$this->db->distinct();
$this->db->select('country');
$this->db->from('distributors');
$this->db->where('country != ', '');
$this->db->order_by("(CASE country WHEN 'UNITED STATES OF AMERICA' THEN '1' ELSE country END)");
回答3:
Since DataMapper doesn't support MYSQL's CASE keyword, the direct solution is to invoke SQL using the query()
method:
$sql = "SELECT * FROM `countries` ORDER BY CASE `name` WHEN 'Australia' THEN 1 ELSE 2 END, `name`";
$countries = new Country();
$countries->query($sql);
来源:https://stackoverflow.com/questions/11821503/does-codeigniter-datamapper-orm-support-a-mysql-case-statement-in-order-by-claus