AdventureWorks Database: Return the difference in sales quotas for a specific employee over previous years

SQL Query - AdventureWorks: Exercise-104 with Solution

104. From the following table write a query in SQL to return the difference in sales quotas for a specific employee over previous years. Returun BusinessEntityID, sales year, current quota, and previous quota.

businessentityid|quotadate              |salesquota|rowguid                             |modifieddate           |
----------------+-----------------------+----------+------------------------------------+-----------------------+
             274|2011-05-31 00:00:00.000|     28000|99109bbf-8693-4587-bc23-6036ec89e1be|2011-04-16 00:00:00.000|
             274|2011-08-31 00:00:00.000|      7000|dfd01444-8900-461c-8d6f-04598dae01d4|2011-07-17 00:00:00.000|
             274|2011-12-01 00:00:00.000|     91000|0a69f453-9689-4ccf-a08c-c644670f5668|2011-10-17 00:00:00.000|
             274|2012-02-29 00:00:00.000|    140000|da8d1458-5fb9-4c3e-9ead-8f5ce1393047|2012-01-15 00:00:00.000|
             274|2012-05-30 00:00:00.000|     70000|760cef84-b980-417b-a667-7358c38857f0|2012-04-15 00:00:00.000|
             274|2012-08-30 00:00:00.000|    154000|fb29e024-f26a-49aa-a7cc-c99ae7ba4853|2012-07-16 00:00:00.000|
             274|2012-11-30 00:00:00.000|    107000|13947d2c-a254-47c9-8817-cbd186ffa526|2012-10-16 00:00:00.000|
             274|2013-02-28 00:00:00.000|     58000|bc1a222f-47a0-48d1-9c56-ac873269dc98|2013-01-14 00:00:00.000|
             274|2013-05-30 00:00:00.000|    263000|8b4e3cbf-f0ef-49c5-9a8c-87679055057e|2013-04-15 00:00:00.000|
             274|2013-08-30 00:00:00.000|    116000|e9de95e3-b119-4441-bd1d-b27fc4516022|2013-07-16 00:00:00.000|
             274|2013-11-30 00:00:00.000|     84000|7cea47b5-8391-4414-a866-ff6ec6628cd3|2013-10-16 00:00:00.000|
             274|2014-03-01 00:00:00.000|    187000|0cfb6474-20aa-46d3-a5c0-29dba2eda025|2014-01-15 00:00:00.000|
-- more --

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Sample Solution:

-- Selecting the business entity ID, sales year, current quota, and previous quota for a specific salesperson
SELECT BusinessEntityID, date_part('year',QuotaDate) AS SalesYear, SalesQuota AS CurrentQuota,   
       LAG(SalesQuota, 1,0) OVER (ORDER BY date_part('year',QuotaDate)) AS PreviousQuota  
-- From the Sales.SalesPersonQuotaHistory table
FROM Sales.SalesPersonQuotaHistory  
-- Filtering the data for a specific salesperson and specific years
WHERE BusinessEntityID = 275 AND date_part('year',QuotaDate) in (2012,2013);

Explanation:

• This SQL query retrieves the business entity ID, sales year, current quota, and previous quota for a specific salesperson for the years 2012 and 2013.
• The SELECT clause specifies the columns to be retrieved, including the sales year calculated from the QuotaDate, the current quota, and the previous quota.
• The FROM clause indicates the source table from which the data will be retrieved, which is the SalesPersonQuotaHistory table.
• The WHERE clause filters the data for a specific salesperson with BusinessEntityID 275 and limits the sales years to 2012 and 2013.
• The LAG window function retrieves the value of SalesQuota from the previous row within the ordered partition specified by the ORDER BY clause.

Sample Output:

businessentityid|salesyear|currentquota|previousquota|
----------------+---------+------------+-------------+
             275|   2012.0|      550000|            0|
             275|   2012.0|     1429000|       550000|
             275|   2012.0|     1324000|      1429000|
             275|   2012.0|      729000|      1324000|
             275|   2013.0|     1194000|       729000|
             275|   2013.0|     1575000|      1194000|
             275|   2013.0|     1218000|      1575000|
             275|   2013.0|      849000|      1218000|

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