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

SQL Query - AdventureWorks: Exercise-181 with Solution

181. From the following table write a query in SQL to return the difference in sales quotas for a specific employee over previous calendar quarters. Sort the results by salesperson with businessentity id 277 and quotadate year 2012 or 2013.

Sample table: sales.salespersonquotahistory

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 quotadate as Year, and extracting the quarter from the quotadate
SELECT quotadate AS Year, date_part('quarter',quotadate) AS Quarter, SalesQuota AS SalesQuota,  
       -- Retrieving the previous sales quota using the LAG window function
       LAG(SalesQuota) OVER (ORDER BY date_part('year',quotadate), date_part('quarter',quotadate)) AS PrevQuota,  
       -- Calculating the difference between the current sales quota and the previous sales quota
       SalesQuota - LAG(SalesQuota) OVER (ORDER BY date_part('year',quotadate), date_part('quarter',quotadate)) AS Diff  
-- Selecting from the salespersonquotahistory table
FROM sales.salespersonquotahistory  
-- Filtering records where businessentityid is 277 and year is either 2012 or 2013
WHERE businessentityid = 277 AND date_part('year',quotadate) IN (2012, 2013)  
-- Ordering the results by year and quarter
ORDER BY date_part('year',quotadate), date_part('quarter',quotadate);

Explanation:

• This SQL query analyzes sales quota history for a specific salesperson.
• Comments are added to explain each part of the query for better understanding and maintenance.
• Here's a breakdown of what the query does:
• It selects the quotadate as Year and extracts the quarter from the quotadate.
• It retrieves the sales quota for each quarter.
• It uses the LAG window function to fetch the previous sales quota based on the ordering by year and quarter.
• It calculates the difference between the current sales quota and the previous sales quota.
• It filters records for a specific salesperson (businessentityid = 277) and for years 2012 and 2013.
• It orders the results by year and quarter.

Sample Output:

year                   |quarter|salesquota|prevquota|diff   |
-----------------------+-------+----------+---------+-------+
2012-02-29 00:00:00.000|    1.0|    952000|         |       |
2012-05-30 00:00:00.000|    2.0|   1600000|   952000| 648000|
2012-08-30 00:00:00.000|    3.0|   1352000|  1600000|-248000|
2012-11-30 00:00:00.000|    4.0|    839000|  1352000|-513000|
2013-02-28 00:00:00.000|    1.0|   1369000|   839000| 530000|
2013-05-30 00:00:00.000|    2.0|   1171000|  1369000|-198000|
2013-08-30 00:00:00.000|    3.0|    971000|  1171000|-200000|
2013-11-30 00:00:00.000|    4.0|    714000|   971000|-257000|

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