Question

I’m trying to improve a routine in my program where I’m counting the number of occurrences of the same date.
So maybe an example:

Time         Other_stuff Entry
1332334357   .....
1332334367   .....
1332334386   .....

Till now I’ve used a statement like :

 SELECT date(time, 'unixepoch') FROM reviewHistory 
        WHERE lastInterval <= 21 AND nextInterval > 21

Now I basically want to generate a histogram of the entries falling on the same date

2012-03-21 20
2012-03-20 13
2012-03-19 50

And so on. However I don’t see an easy way to do this so I figured I would simply do a SELECT DISTINCT and store those values and then query for each distinct entry with the conditionals and check the row count. It’d save me processing time and I/O access time however I haven’t been able to find a statement that accomplishes this. I thought something like this would work but it doesn’t. Example:

SELECT time FROM reviewHistory WHERE
(SELECT date(time, 'unixepoch') FROM reviewHistory
        WHERE lastInterval <= 21 AND nextInterval > 21) = "2012-03-21"

It doesn’t error but it also doesn’t return anything and I feel pretty sure that this is something that I should be able to accomplish in a few SQLite statements and not have to manage application side.

UPDATE: Lol it just came to me after I posted it. Though I still want to believe there’s a more graceful way to accomplish the tallying problem in SQL.

SELECT time FROM 
       (SELECT date(time, 'unixepoch') AS time 
       FROM reviewHistory WHERE lastInterval <= 21 AND nextInterval > 21)
  WHERE time = "2012-03-21"

Answer 1

I’m not sure if I understand your question, but to get all dates and the counts, one query should be sufficient:

SELECT date(time, 'unixepoch'), COUNT(*)
FROM reviewHistory 
WHERE lastInterval <= 21 AND nextInterval > 21
GROUP BY date(time, 'unixepoch')