Question

I have a table with different values for different countries, for example:

id| country  |
===================
1 | Argelia  | 
2 | USA      |
1 | China    |
1 | Italy    |
1 | Italy    |
1 | USA      |
4 | USA      |
1 | Argelia  |

I am interested in only one country’s count, and the total count, but I’m having trouble coming up with a single query to do it. The result of this query for id 1 would be:

id| value_in_Italy | total
==========================
1 | 2              | 6

As you can see, I obtained the value for Italy, and the total value. What kind of query would produce rows like the above for a similar table?

Answer 1

The simplest query that works on MySQL I can think of is:

select id, sum(country = 'Italy') values_in_Italy, count(*) Total from t
where id = 1

MySQL doesn’t force you to group by id as it will non-deterministically take one id, but the where clause is forcing that column to only have one id