Finding duplicate in SQL Server Table

Question

I have a table

+--------+--------+--------+--------+--------+
| Market | Sales1 | Sales2 | Sales3 | Sales4 |
+--------+--------+--------+--------+--------+
|            


        

Answer 1

This problem would be incredibly simple to solve if you normalised your table.

Then you would just have the columns Market | Sales, or if the 1, 2, 3, 4 are important you could have Market | Quarter | Sales (or some other relevant column name).

Given that your table isn't in this format, you could use a CTE to make it so and then select from it, e.g.

WITH cte AS (
    SELECT Market, Sales1 AS Sales FROM MarketSales
    UNION ALL 
    SELECT Market, Sales2 FROM MarketSales
    UNION ALL 
    SELECT Market, Sales3 FROM MarketSales
    UNION ALL 
    SELECT Market, Sales2 FROM MarketSales
)
SELECT a.Market
      ,b.Market
FROM cte a
INNER JOIN cte b ON b.Market > a.Market
WHERE a.Sales = b.Sales

You can easily do this without the CTE, you just need a big where clause comparing all the combinations of Sales columns.