Create Pivot Table using PostgreSQL - postgresql

Question

I have a table like this:
type code desc store Sales/Day Stock
-----------------------------------------------
1 AA1 abc 101 3 6
1 AA2 abd 101 4 0
1 AA3 abf 101 4 3
2 BA1 bba 101 5 1
2 BA2 bbc 101 2 1
1 AA1 abc 102 1 4
1 AA2 abd 102 2 0
2 BA1 bba 102 4 2
2 BA2 bbc 102 5 5
etc.
How I can show the result table like this:
type code desc Store 101 Store 102
Sales/Day | Stock Sales/Day | Stock
--------------------------------------------------------------
1 AA1 abc 3 6 1 4
1 AA2 abd 4 0 2 0
1 AA3 abf 4 3 0 0
2 BA1 bba 5 1 4 2
2 BA2 bbc 2 1 5 5
etc.
Note:
Colspan is only display.

Answer 1

demo:db<>fiddle
First way: FILTER
SELECT
type,
code,
"desc",
COALESCE(SUM(sales_day) FILTER (WHERE store = 101)) as sales_day_101,
COALESCE(SUM(stock) FILTER (WHERE store = 101), 0) as stock_101,
COALESCE(SUM(sales_day) FILTER (WHERE store = 102), 0) as sales_day_102,
COALESCE(SUM(stock) FILTER (WHERE store = 102), 0) as stock_102
FROM mytable
GROUP BY type, code, "desc"
ORDER BY type, code
Aggregating your values. I took SUM but in your case with distinct rows many other aggregate functions would do it. FILTER allows you to aggregate only one store.
The COALESCE is to avoid NULL values if no values are present for one aggregation (like AA3 in store 102).
Second way, CASE WHEN
SELECT
type,
code,
"desc",
SUM(CASE WHEN store = 101 THEN sales_day ELSE 0 END) as sales_day_101,
SUM(CASE WHEN store = 101 THEN stock ELSE 0 END) as stock_101,
SUM(CASE WHEN store = 102 THEN sales_day ELSE 0 END) as sales_day_102,
SUM(CASE WHEN store = 102 THEN stock ELSE 0 END) as stock_102
FROM mytable
GROUP BY type, code, "desc"
ORDER BY type, code
The idea is the same, but the newer FILTER function is replace by the more common CASE clause.
Notice that "desc" is a reserved word in Postgres. So I strictly recommend to rename your column.