Fetching records from one table with different conditions

Question

Hi i am working with postgresql database. I need to calculate the average time between the records what i am fetching from one table.

Schema:

create_table "user"  do |t|
t.text     "status"
t.datetime "time"
t.datetime "updated_at"

end

Example:

1. select time from users where status = 'now';
2. select time from users where status = 'after';

on results of above queries i need to perform average time. Probably i need to combine those two queries into one query. I tried with union operator, whether it is right way to use?. So any help is appreciated..

Answer 1

You should consider using SQL SELECT AVG() function, for each group. eg,

select status, avg(time)  from users where status = 'now' or status = 'after' group by status