1. There are several tables with exactly the same structure. I want to summarize these tables by a certain field.
Reference blog: http://blog.csdn.net/vinson0526/article/details/9367469
such as table upc1:
| application | count |
|---|---|
| http | 3 |
| ftp | 4 |
| www | 10 |
Table upc2 :
| application | count |
|---|---|
| http | 7 |
| ftp | 6 |
| www | 13 |
Finally, I want to get the following table tt:
| application | count |
|---|---|
| http | 10 |
| ftp | 10 |
| www | 23 |
Code:
select application, sum(count) from (
select * from upc1
union all
select * from upc2) tt
group by applicaton;
Summary: union and union all can be used to merge tables with the same structure.