= Monthly sales and profit per store

=== Description
This view provides a monthly overview of sales and profit for each store by combining information from the REPORT, STORE, and exchanges_data tables.

The view is intended for:

- monitoring monthly store performance
- financial reports
- comparing stores
- analyzing sales and profit trends

==== Tables covered by the view:

- Report
- Store
- exchanges_data

==== SQL код
{{{#!sql
CREATE OR REPLACE VIEW vw_monthly_sales_profit AS
SELECT
    s.store_id,
    s.name AS store_name,
    r.date,
    r.month_and_year,
    r.profit,
    r.overall_profit,
    ed.monthly_profit,
    ed.sales,
    ed.damages

FROM store s
JOIN report r
    ON r.store_id = s.store_id
LEFT JOIN exchanges_data ed
    ON ed.store_id = r.store_id
    AND ed.date = r.date;

}}}

==== Logic explanation
**1.** The store information is retrieved from `store`.

**2.** The `report` table provides the monthly profit and overall profit.

**3.** The `exchanges_data` table provides monthly profit, sales, and damages.

**4.** LEFT JOIN is used for `exchanges_data` so that a report is still displayed even if no corresponding data exchange record exists.

**5.** Each row represents the financial information for a particular store and reporting date.

==== Reason for view 
This view is useful because:

- It centralizes monthly financial information
- It simplifies financial reporting queries
- It allows easy comparison of store performance
- It provides sales, profit, and damages in one result
- It reduces repeated JOIN operations in the application

Without this view, when doing any analitical tasks system will have to make multiple joints to get the results.