MySQL SUM同一行中的多个列

Question

+---------------+---------+-----------------+---------+ 
| product_count | size1   | sproduct_count2 | size2
+---------------+---------+-----------------+---------+ 
|            13 | 2x4     |               5 |     2x6 
|            14 | 2x6     |               2 |     4x8 
|            15 | 2x8     |               3 |     2x8 
|            16 | 4x4     |               2 |     4x4 
|            17 | 4x8     |              15 |     4x8
+---------------+---------+-----------------+---------+

How do I get the total counts so the return results appear like:

product_count | size
           13 | 2x4
           19 | 2x6
           18 | 2x8
           18 | 4x4
           34 | 4x8

I have tried:

SELECT SUM(product_count+product_count2) AS product_count, size1 FROM UNITS GROUP BY size1

and it works for some rows and others it does not work for. Would CONCAT be something I need to use?

Answer 1

You need to aggregate on the union of the 2 columns:

select sum(t.product_count) product_count, t.size from (
  select product_count, size1 size from units
  union all
  select sproduct_count2, size2 from units
) t
group by t.size

See the demo .
Results:

| product_count | size |
| ------------- | ---- |
| 13            | 2x4  |
| 19            | 2x6  |
| 18            | 2x8  |
| 18            | 4x4  |
| 34            | 4x8  |

Answer 2

select u1.product_count + if(u2.product_count is null,0,u2.product_count) as product_count,u1.size1 as size
from units u1
left join (select sum(sproduct_count2) as product_count,size2 
from units
group by size2) u2
on u1.size1 = u2.size2;

Demo: https://www.db-fiddle.com/f/8TfoNen5toVHvy4DbBe7M6/0

• You could first sum up all counts from sproduct_count2 with size2 with a group by on size2 .
• You could then do a left join on the above result with the units table itself with an additional if condition check if in case you find a size1 not there in size2 (in which case you could add a 0).

Note: This only filters values appearing in size1 (with it's appropriate counts) looking at the query you tried ( SUM(product_count+product_count2) AS product_count, size1 FROM )