Question

I have a table which is randomly generated. It has 3 columns : P_Id, date (at which the row was inserted) and text. Let’s say the text can be various animals. So the table could look like

1      2011-06-15 03:04:05    cow  
2      2011-06-15 03:04:15    dog  
3      2011-06-15 03:04:19    bird  
4      2011-06-15 03:04:30    cow  
5      2011-06-15 03:04:30    dog  
6      2011-06-15 03:04:35    cow  
....  

What is a query to pick all animals that have occurred at least twice within the last 30 minutes of its latest entry? For eg, here cow occurs 3 times within the last 30 minutes of its latest entry, which is at 3:04:35, and dog has occurred twice. Bird would not be selected as it only occurred once.

Answer 1

There’s always the straight forward way (i.e. use a subquery to extract the timestamp range and then proceed as usual):

select name, count(name)
from your_table
where created_at >= (
    select max(created_at) - INTERVAL 30 MINUTE
    from your_table
)
group by name
having count(name) >= 2