how to calculate prevalence using sql code

Question

I am trying to calculate prevalence in sql. kind of stuck in writing the code. I want to make automative code.

I have check that I have 1453477 of sample size and numbe

Answer 1

In your current query you count the number of rows in the disease table, once using the column condition_id, once using the column person_id. But the number of rows is the same - this is why you get 1 as a result.

I think you need to find the number of different values for these columns. This can be done using count distinct:

select (COUNT(DISTINCT condition_id)/COUNT(DISTINCT person_id)) as prevalence
from disease
where condition_id=12345;