Example crosstab function

gistfile1.sql

SELECT c.id, c.name, c.jan, c.feb, c.mar
FROM crosstab(
  'select buyers.id, buyers.name, transactions.month, sum(transactions.amount) from transactions inner join buyers on buyers.id = transactions.buyer_id group by buyers.id, buyers.name, transactions.month order by buyers.id, transactions.month',
  'select generate_series(1, 3)'
) c (id integer, name character varying, jan numeric(12,2), feb numeric(12,2), mar numeric(12,2));