Produce a summary (“pivot”?) table

Question

I\'d like a way to summarise a database table so that rows sharing a common ID are summarised into one row of output.

My tools are SQLite and Python 2.x.

For

Answer 1

On python side, you could use some itertools magic for rearranging your data:

data = [('Apple',      'Coles',      1.50),
        ('Apple',      'Woolworths', 1.60),
        ('Apple',      'IGA',        1.70),
        ('Banana',     'Coles',      0.50),
        ('Banana',     'Woolworths', 0.60),
        ('Banana',     'IGA',        0.70),
        ('Cherry',     'Coles',      5.00),
        ('Date',       'Coles',      2.00),
        ('Date',       'Woolworths', 2.10),
        ('Elderberry', 'IGA',        10.00)]

from itertools import groupby, islice
from operator import itemgetter
from collections import defaultdict

stores = sorted(set(row[1] for row in data))
# probably splitting this up in multiple lines would be more readable
pivot = ((fruit, defaultdict(lambda: None, (islice(d, 1, None) for d in data))) for fruit, data in groupby(sorted(data), itemgetter(0)))

print 'Fruit'.ljust(12), '\t'.join(stores)
for fruit, prices in pivot:
    print fruit.ljust(12), '\t'.join(str(prices[s]) for s in stores)

---

Output:

Fruit        Coles      IGA     Woolw
Apple        1.5        1.7     1.6
Banana       0.5        0.7     0.6
Cherry       5.0        None    None
Date         2.0        None    2.1
Elderberry   None       10.0    None