如何使用MySQL Group选择多个记录？

Question

I can't seem to use distinct or group by to group certain mySQL records together. This SQL query below just returns one line each - I want all the values in the CID though..

I want to select a random group by cid or the first set in the table.. I cant use AND CID=X .. is there a way to do it without ..

Table

id      pid     image                           sort_order      cid
-----
2474    50      data/low.jpg            2                       56
2473    50      data/hi.jpg             3                       59
2471    50      data/thumn.jpg      500                     59
2472    50      data/front.jpg      1000                    56
2470    50      data/back.jpg           1                       56

Query

SELECT *
FROM `ocm1__product_image`
WHERE `product_id` = '50'
GROUP BY `cid`
ORDER BY `ocm1__product_image`.`sort_order` ASC
LIMIT 0 , 30

This should return

id      pid     image                           sort_order      cid
2474    50      data/low.jpg            2                       56
2472    50      data/front.jpg      1000                    56
2470    50      data/back.jpg           1                       56

But it returns both colours.. can I not unique the group?

It returns this which is wrong, I want to list all cid unique values

id      pid     image                           sort_order      cid
2474    50      data/low.jpg            2                       56
2471    50      data/thumn.jpg      500                     59

Answer 1

This will return all the entries with the lowest cid for the requested pid .
It gives the same result as you say that you need, without giving a specific cid as a condition;

SELECT o1.*
FROM `ocm1__product_image` o1
LEFT JOIN `ocm1__product_image` o2
  ON o1.pid=o2.pid AND o1.cid > o2.cid
WHERE o1.`pid` = '50' AND o2.cid IS NULL
ORDER BY `o1`.`sort_order` ASC
LIMIT 0 , 30

An SQLfiddle to test with .

Answer 2

Don't use group by to sort them, you just need to use order by in addition you must also sort them using the CID value for specific Customer ID only, You have the value Product ID (PID) but you didn't provide the CID value into your samples.

SELECT *
FROM `ocm1__product_image`
WHERE `product_id` = '50' and `cid` = '56'
ORDER BY `ocm1__product_image`.`sort_order` ASC
LIMIT 0 , 30

---

or if you want to sort them using the ID , to know where is the first data inserted by using the primary key

SELECT *
FROM `ocm1__product_image`
WHERE `product_id` = '50' and `cid` = '56'
ORDER BY `ocm1__product_image`.`id` ASC
LIMIT 0 , 30