postgresql 中的 SQL 查询以生成数据透视表报告以将列转换为行

Question

Unsure how to create a pivot report query in postgres (newbie to postgres) based on the following tables/report layout.

Please note that I am not able to change the structure of these tables as out of my control.

STOCK_REF ( sr_id, stock_name )

STOCK_INVENTORY ( si_id, sr_id, stock_count ) * where sr_id here is a foreign key constraint

Sample data for each table may include the following:

STOCK_REF
1 GUITAR
2 BASS
3 DRUMS
4 KEYBOARDS

STOCK_INVENTORY
1 1 10
2 2 5
3 3 2
4 4 15

Using the above two tables, I need to produce a report that looks like:

STOCK NAME                  COUNT
--------------------------- --------
GUITAR                      10
BASS                        5
DRUMS                       2
KEYBOARDS                   15

which is like a pivot table.

The thing is, I can write the query that will produce the stock name as columns with counts but I actually need to have the stock name and counts as rows, like above.

Any help with this postgres query would be ideal

Answer 1

Try the query below. It's simple SQL. I think POSTGRES don't determine too much here...

SELECT stock_name AS "STOCK NAME", stock_count AS "COUNT"
FROM STOCK_REF INNER JOIN STOCK_INVENTORY
ON (STOCK_REF.sr_id = STOCK_INVENTORY.sr_id)