Q1795 added.

SQL/Q1795.sql

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+--Table: Products
+
+--+-------------+---------+
+--| Column Name | Type    |
+--+-------------+---------+
+--| product_id  | int     |
+--| store1      | int     |
+--| store2      | int     |
+--| store3      | int     |
+--+-------------+---------+
+--product_id is the primary key for this table.
+--Each row in this table indicates the product's price in 3 different stores: store1, store2, and store3.
+--If the product is not available in a store, the price will be null in that store's column.
+
+
+--Write an SQL query to rearrange the Products table so that each row has (product_id, store, price). 
+--If a product is not available in a store, do not include a row with that product_id and store combination in the result table.
+
+
+/* Write your T-SQL query statement below */
+select product_id, 'store1' as store, store1 as price from Products p 
+where store1 is not NULL
+UNION
+select product_id, 'store2' as store, store2 as price from Products p
+where store2 is not NULL
+UNION
+select product_id, 'store3' as store, store3 as price from Products p 
+where store3 is not NULL