SQL如何对COUNT检索的字段求和？

Question

This is what I tried, but it didnt work.

Select customer_id, sum(count (contact_id), count (call_id))
from contacts
limit 10

Answer 1

If you are trying to add together the count of contact_ids and call_ids you can simply use + between the two fields

Select customer_id, count (contact_id)+count (call_id)
from contacts
limit 10

Answer 2

Select customer_id, count (contact_id) + count (call_id)
from contacts
limit 10

you may need a GROUP BY clause unless your db adds one for you (mysql in certain configurations)