如何在 JOINED 表的 SQL UNION 中 ORDER BY 未在结果中显示有序列

Question

I'm trying to get the table where two results of joins will be unioned and ordered by several columns. I've found that columns that are ordered have to be mentioned in each select of union. But I don't want ordered columns appear in result. Is it possible? Maybe there are another ways of getting the result that I want.

Here is my query:

SELECT coupon_id,
       coupon_name,
       real_price,
       discount_price,
       difference_percent,
       discount_percent,
       payment_price,
       photo,
       company_id,
       company_name
FROM
  (SELECT cpn.id AS coupon_id,
          cpn.name_ru AS coupon_name,
          cpn.real_price,
          cpn.discount_price,
          cpn.difference_percent,
          cpn.discount_percent,
          cpn.payment_price,
          cp.photo,
          com.id company_id,
          com.name_ru AS company_name
   FROM coupon cpn
   LEFT JOIN coupon_photo cp ON cpn.id = cp.coupon_id
   LEFT JOIN company com ON cpn.company_id = com.id
   WHERE cpn.id NOT IN
       (SELECT coupon_id AS id
        FROM transaction
        WHERE Date_add(created_time, interval 10 MINUTE) > Now()
          AND status = 'pending')
     AND cpn.exp_date > Now()
     AND cpn.valid_date > Now()
     AND cpn.available > 0
   UNION SELECT cpn.id AS coupon_id,
                cpn.name_ru AS coupon_name,
                cpn.real_price,
                cpn.discount_price,
                cpn.difference_percent,
                cpn.discount_percent,
                cpn.payment_price,
                cp.photo,
                com.id company_id,
                com.name_ru AS company_name
   FROM coupon cpn
   LEFT JOIN coupon_photo cp ON cpn.id = cp.coupon_id
   LEFT JOIN company com ON cpn.company_id = com.id
   LEFT JOIN transaction trans ON cpn.id = trans.coupon_id
   WHERE cpn.exp_date > Now()
     AND cpn.valid_date > Now()
     AND Date_add(trans.created_time, interval 10 MINUTE) > NOW()
     AND trans.status = 'pending'
     AND (cpn.available - trans.amount) > 0 GROUP  BY cpn.id) results
ORDER BY cpn.advertised DESC,
         cpn.sold DESC,
         cpn.views DESC

Answer 1

Your results subquery does not contain the column you are trying to order by . You need to add them to both parts of the union. You do not have to add them to your select, but they need to be present in the subquery so you can use them in your ORDER BY .

SELECT coupon_id,
       coupon_name,
       real_price,
       discount_price,
       difference_percent,
       discount_percent,
       payment_price,
       photo,
       company_id,
       company_name
FROM
  (SELECT cpn.id AS coupon_id,
          cpn.name_ru AS coupon_name,
          cpn.real_price,
          cpn.discount_price,
          cpn.difference_percent,
          cpn.discount_percent,
          cpn.payment_price,
          cp.photo,
          cpn.advertised,
          cpn.sold,
          cpn.views,
          com.id company_id,
          com.name_ru AS company_name
   FROM coupon cpn
   LEFT JOIN coupon_photo cp ON cpn.id = cp.coupon_id
   LEFT JOIN company com ON cpn.company_id = com.id
   WHERE cpn.id NOT IN
       (SELECT coupon_id AS id
        FROM transaction
        WHERE Date_add(created_time, interval 10 MINUTE) > Now()
          AND status = 'pending')
     AND cpn.exp_date > Now()
     AND cpn.valid_date > Now()
     AND cpn.available > 0
   UNION SELECT cpn.id AS coupon_id,
                cpn.name_ru AS coupon_name,
                cpn.real_price,
                cpn.discount_price,
                cpn.difference_percent,
                cpn.discount_percent,
                cpn.payment_price,
                cp.photo,
                cpn.advertised,
                cpn.sold,
                cpn.views,
                com.id company_id,
                com.name_ru AS company_name
   FROM coupon cpn
   LEFT JOIN coupon_photo cp ON cpn.id = cp.coupon_id
   LEFT JOIN company com ON cpn.company_id = com.id
   LEFT JOIN transaction trans ON cpn.id = trans.coupon_id
   WHERE cpn.exp_date > Now()
     AND cpn.valid_date > Now()
     AND Date_add(trans.created_time, interval 10 MINUTE) > NOW()
     AND trans.status = 'pending'
     AND (cpn.available - trans.amount) > 0 GROUP  BY cpn.id) results
ORDER BY advertised DESC,
         sold DESC,
         views DESC

As Strawberry has pointed out, it is not exactly best practice o use GROUP BY when you are not aggregating anything. In this case it can lead to unexpected results as MySQL uses ANY_VALUE(). It returns the value of some row in the GROUP BY group. Which row it returns is indeterminate. That means it's entirely up to the MySQL server.

I assume you were using it to avoid duplicate rows. You should find another de-duplication method.

Furthermore, doing a LEFT JOIN but then filtering the elements on the right side of the JOIN is the same as doing an INNER JOIN. Just make sure this is consistent with what you are trying to achieve.