Question

This is my table definition:

CREATE TABLE orders_total (
  orders_total_id int unsigned NOT NULL auto_increment,
  orders_id int NOT NULL,
  title varchar(255) NOT NULL,
  text varchar(255) NOT NULL,
  value decimal(15,4) NOT NULL,
  class varchar(32) NOT NULL,
  sort_order int NOT NULL,
  PRIMARY KEY (orders_total_id),
  KEY idx_orders_total_orders_id (orders_id)
);

A populated table can look something like this (all made-up numbers from my memory):

1 - 13 - Shipping - $7.50   - 7.50   - ot_shipping - 2
2 - 13 - Tax      - $8.00   - 8.00   - ot_tax      - 4
3 - 13 - Total    - $56.67  - 56.67  - ot_total    - 3
4 - 14 - Shipping - $5.55   - 5.55   - ot_shipping - 2
5 - 14 - Discount - $6.40   - 6.40   - ot_discount - 1
6 - 14 - Coupon   - $10.00  - 10.00  - ot_coupon   - 5
7 - 14 - Total    - $150.25 - 150.25 - ot_total    - 3

Every order can have different classes, and not all orders have to have the exact number of classes. For example:

1. Order 1 can have the following classes: ot_shipping, ot_tax, ot_total
2. Order 2 can have the following classes: ot_shipping, ot_discount, ot_coupon, ot_total
3. …

I’d like to write a query that queries my orders table (not displayed here), and joins the above table (orders_total), and grabs the “value” column only if the “class” is either “ot_total”, “ot_coupon”, or “ot_discount”.

Here is my attempt at creating such a query:

SELECT o.orders_id, o.customers_name, group_concat(ot.value) AS values
FROM orders o
LEFT JOIN orders_total ot
ON ot.orders_id = o.orders.id
GROUP BY o.orders_id

The above query would produce something like this:

First set of results:

orders_id      => 13
customers_name => John Doe
values         => 7.50,8.00,56.67

Second set of results:

orders_id      => 14
customers_name => Jane Roe
values         => 5.55,6.40,10.00,150.25

As you can see, the values gives me what I need, but I just don’t know what number belongs to which class. I’m only interested in ot_total, ot_discount, and ot_coupon.

Anybody can think of any solution?

Is it possible to somehow append the class name to the values as well? So I can have something like values => ot_shippimh7.50,ot_tax8.00,ot_total56.67

Answer 1

You can do this:

SELECT o.orders_id, o.customers_name,
       GROUP_CONCAT(CONCAT( ot.class, ot.value)) AS values
FROM orders o
LEFT JOIN orders_total ot
ON ot.orders_id = o.orders.id
WHERE ot.class in ("ot_total", "ot_coupon", "ot_discount")
GROUP BY o.orders_id

BTW: You can do better, by remove the class field from your orders_total, add a new table called Classes instead that contains a list of classes then add a foreign key reference to this table to your orders_total.