Question

Trying to write a function to see how often an object exists and give it a + 1 based on the number of times it exists.

Using sqlite database and python.

select distinct Date, Name from history order by Date Desc

Will return:

Date        Name
2012-25-03     a
2012-25-03     b
2012-25-03     c
2012-25-03     d
2012-24-03     b
2012-24-03     c
2012-24-03     d
2012-24-03     e
2012-23-03     c
2012-23-03     d
2012-23-03     e
2012-23-03     f

Basically looking to accomplish the following in either python or sql:

a = 1
b = 2
c = 3
d = 3
e = 2
f = 1

I have attempted a few different approaches in python using iterators and subqueries, but haven’t been successful, maybe it can/should be done is sql.

Appreciate everyone’s time!

Answer 1

SELECT Name
     , COUNT(*) AS cnt
FROM history 
GROUP BY Name
ORDER BY Name

If there is a chance you have more than one row with same Date and Name and you don’t want to doubly count those rows, change the COUNT(*) to:

     , COUNT(DISTINCT Date) AS cnt

---

(update) If your SQLite version does not support COUNT(DISTINCT column), you could use a subquery in that case:

SELECT Name
     , COUNT(*) AS cnt
FROM 
    ( SELECT DISTINCT
          Name, Date
      FROM history 
    ) AS h 
GROUP BY Name
ORDER BY Name