AdventureWorks Database: Order table conditionally using case statement

SQL Query - AdventureWorks: Exercise-33 with Solution

33. From the following table write a query in SQL to set the result in order by the column TerritoryName when the column CountryRegionName is equal to 'United States' and by CountryRegionName for all other rows.

businessentityid|territoryid|salesquota|bonus|commissionpct|salesytd    |saleslastyear|rowguid                             |modifieddate           |
----------------+-----------+----------+-----+-------------+------------+-------------+------------------------------------+-----------------------+
             274|           |          |    0|            0| 559697.5639|            0|48754992-9ee0-4c0e-8c94-9451604e3e02|2010-12-28 00:00:00.000|
             275|          2|    300000| 4100|        0.012|3763178.1787| 1750406.4785|1e0a7274-3064-4f58-88ee-4c6586c87169|2011-05-24 00:00:00.000|
             276|          4|    250000| 2000|        0.015|4251368.5497| 1439156.0291|4dd9eee4-8e81-4f8c-af97-683394c1f7c0|2011-05-24 00:00:00.000|
             277|          3|    250000| 2500|        0.015|3189418.3662| 1997186.2037|39012928-bfec-4242-874d-423162c3f567|2011-05-24 00:00:00.000|
             278|          6|    250000|  500|         0.01|1453719.4653| 1620276.8966|7a0ae1ab-b283-40f9-91d1-167abf06d720|2011-05-24 00:00:00.000|
             279|          5|    300000| 6700|         0.01| 2315185.611| 1849640.9418|52a5179d-3239-4157-ae29-17e868296dc0|2011-05-24 00:00:00.000|
             280|          1|    250000| 5000|         0.01|1352577.1325|  1927059.178|be941a4a-fb50-4947-bda4-bb8972365b08|2011-05-24 00:00:00.000|
             281|          4|    250000| 3550|         0.01|2458535.6169| 2073505.9999|35326ddb-7278-4fef-b3ba-ea137b69094e|2011-05-24 00:00:00.000|
             282|          6|    250000| 5000|        0.015|2604540.7172| 2038234.6549|31fd7fc1-dc84-4f05-b9a0-762519eacacc|2011-05-24 00:00:00.000|
             283|          1|    250000| 3500|        0.012|1573012.9383| 1371635.3158|6bac15b2-8ffb-45a9-b6d5-040e16c2073f|2011-05-24 00:00:00.000|
             284|          1|    300000| 3900|        0.019|1576562.1966|            0|ac94ec04-a2dc-43e3-8654-dd0c546abc17|2012-09-23 00:00:00.000|
             285|           |          |    0|            0| 172524.4512|            0|cfdbef27-b1f7-4a56-a878-0221c73bae67|2013-03-07 00:00:00.000|
             286|          9|    250000| 5650|        0.018|1421810.9242| 2278548.9776|9b968777-75dc-45bd-a8df-9cdaa72839e1|2013-05-23 00:00:00.000|
             287|           |          |    0|            0|  519905.932|            0|1dd1f689-df74-4149-8600-59555eef154b|2012-04-09 00:00:00.000|
             288|          8|    250000|   75|        0.018|1827066.7118| 1307949.7917|224bb25a-62e3-493e-acaf-4f8f5c72396a|2013-05-23 00:00:00.000|
             289|         10|    250000| 5150|         0.02|4116871.2277| 1635823.3967|25f6838d-9db4-4833-9ddc-7a24283af1ba|2012-05-23 00:00:00.000|
             290|          7|    250000|  985|        0.016|3121616.3202| 2396539.7601|f509e3d4-76c8-42aa-b353-90b7b8db08de|2012-05-23 00:00:00.000|

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Sample Solution:

-- Selecting specific columns from the vSalesPerson view
SELECT BusinessEntityID, LastName, TerritoryName, CountryRegionName  

-- From the Sales schema's vSalesPerson view
FROM Sales.vSalesPerson  

-- Filtering the results to include only rows where TerritoryName is not NULL
WHERE TerritoryName IS NOT NULL  

-- Ordering the results using a conditional CASE statement
-- If CountryRegionName is 'United States', order by TerritoryName
-- Otherwise, order by CountryRegionName
ORDER BY CASE CountryRegionName WHEN 'United States' THEN TerritoryName  
         ELSE CountryRegionName END;

Explanation:

• The SQL query retrieves data from the vSalesPerson view within the Sales schema.
• It selects four columns: BusinessEntityID, LastName, TerritoryName, and CountryRegionName.
• The WHERE clause filters the results to include only rows where TerritoryName is not NULL.
• The ORDER BY clause specifies the sorting criteria for the result set using a conditional expression.
• The CASE statement checks the value of CountryRegionName. If it is 'United States', the rows are ordered by TerritoryName. Otherwise, they are ordered by CountryRegionName.
• This results in a sorting order where territories within the United States are listed alphabetically by TerritoryName, and territories outside the United States are listed alphabetically by CountryRegionName.

Sample Output:

businessentityid|lastname         |territoryname |countryregionname|
----------------+-----------------+--------------+-----------------+
             286|Tsoflias         |Australia     |Australia        |
             282|Saraiva          |Canada        |Canada           |
             278|Vargas           |Canada        |Canada           |
             277|Carson           |Central       |United States    |
             290|Varkey Chudukatil|France        |France           |
             288|Valdez           |Germany       |Germany          |
             275|Blythe           |Northeast     |United States    |
             280|Ansman-Wolfe     |Northwest     |United States    |
             284|Mensa-Annan      |Northwest     |United States    |
             283|Campbell         |Northwest     |United States    |
             279|Reiter           |Southeast     |United States    |
             276|Mitchell         |Southwest     |United States    |
             281|Ito              |Southwest     |United States    |
             289|Pak              |United Kingdom|United Kingdom   |

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