Sort and Filter Query Results

In this lab, you’ll use the Transact-SQL SELECT statement to query and filter data in the AdventureWorks database. For your reference, the following diagram shows the tables in the database (you may need to resize the pane to see them clearly).

An entity relationship diagram of the adventureworks database

Note: If you’re familiar with the standard AdventureWorks sample database, you may notice that in this lab we are using a simplified version that makes it easier to focus on learning Transact-SQL syntax.

Sort results using the ORDER BY clause

It’s often useful to sort query results into a particular order.

Modify the existing query to return the Name and ListPrice of all products:
```
 SELECT Name, ListPrice
 FROM SalesLT.Product;
```
Run the query and note that the results are presented in no particular order.
Modify the query to add an ORDER BY clause that sorts the results by Name, as shown here:
```
 SELECT Name, ListPrice
 FROM SalesLT.Product
 ORDER BY Name;
```
Run the query and review the results. This time the products are listed in alphabetical order by Name.

Modify the query as shown below to sort the results by ListPrice.

 SELECT Name, ListPrice
 FROM SalesLT.Product
 ORDER BY ListPrice;

Run the query and note that the results are listed in ascending order of ListPrice. By default, the ORDER BY clause applies an ascending sort order to the specified field.
Modify the query as shown below to sort the results into descending order of ListPrice.
```
 SELECT Name, ListPrice
 FROM SalesLT.Product
 ORDER BY ListPrice DESC;
```
Run the query and note that the results now show the most expensive items first.
Modify the query as shown below to sort the results into descending order of ListPrice, and then into ascending order of Name.
```
 SELECT Name, ListPrice
 FROM SalesLT.Product
 ORDER BY ListPrice DESC, Name ASC;
```
Run the query and review the results. Note that they are sorted into descending order of ListPrice, and each set of products with the same price is sorted in ascending order of Name.

Restrict results using TOP

Sometimes you only want to return a specific number of rows. For example, you might want to find the twenty most expensive products.

Modify the existing query to return the Name and ListPrice of all products:

 SELECT TOP (20) Name, ListPrice
 FROM SalesLT.Product
 ORDER BY ListPrice DESC;

Run the query and note that the results contain the first twenty products in descending order of ListPrice. Typically, you include an ORDER BY clause when using the TOP parameter; otherwise the query just returns the first specified number of rows in an arbitrary order.

Modify the query to add the WITH TIES parameter as shown here, and re-run it.

 SELECT TOP (20) WITH TIES Name, ListPrice
 FROM SalesLT.Product
 ORDER BY ListPrice DESC;

This time, there are 21 rows in the results, because there are multiple products that share the same price, one of which wasn’t included when ties were ignored by the previous query.

Modify the query to add the PERCENT parameter as shown here, and re-run it.

 SELECT TOP (20) PERCENT WITH TIES Name, ListPrice
 FROM SalesLT.Product
 ORDER BY ListPrice DESC;

Note that this time the results contain the 20% most expensive products.

Retrieve pages of results with OFFSET and FETCH

User interfaces and reports often present large volumes of data as pages, you make them easier to navigate on a screen.

Modify the existing query to return product Name and ListPrice values:

 SELECT Name, ListPrice
 FROM SalesLT.Product
 ORDER BY Name OFFSET 0 ROWS FETCH NEXT 10 ROWS ONLY;

Run the query and note the effect of the OFFSET and FETCH parameters of the ORDER BY clause. The results start at the 0 position (the beginning of the result set) and include only the next 10 rows, essentially defining the first page of results with 10 rows per page.

Modify the query as shown here, and run it to retrieve the next page of results.

 SELECT Name, ListPrice
 FROM SalesLT.Product
 ORDER BY Name OFFSET 10 ROWS FETCH NEXT 10 ROWS ONLY;

Use the ALL and DISTINCT options

Often, multiple rows in a table may contain the same values for a given subset of fields. For example, a table of products might contain a Color field that identifies the color of a given product. It’s not unreasonable to assume that there may be multiple products of the same color. Similarly, the table might contain a Size field; and again it’s not unreasonable to assume that there may be multiple products of the same size; or even multiple products with the same combination of size and color.

Start Azure Data Studio, and create a new query (you can do this from the File menu or on the welcome page).
In the new SQLQuery_… pane, use the Connect button to connect the query to the AdventureWorks saved connection.
In the query editor, enter the following code:
```
 SELECT Color
 FROM SalesLT.Product;
```
Use the ⏵Run button to run the query, and and after a few seconds, review the results, which includes the color of each product in the table.
Modify the query as follows, and re-run it.
```
 SELECT ALL Color
 FROM SalesLT.Product;
```
The results should be the same as before. The ALL parameter is the default behavior, and is applied implicitly to return a row for every record that meets the query criteria.
Modify the query to replace ALL with DISTINCT, as shown here:
```
 SELECT DISTINCT Color
 FROM SalesLT.Product;
```
Run the modified query and note that the results include one row for each unique Color value. This ability to remove duplicates from the results can often be useful - for example to retrieve values in order to populate a drop-down list of color options in a user interface.

Modify the query to add the Size field as shown here:

 SELECT DISTINCT Color, Size
 FROM SalesLT.Product;

Run the modified query and note that it returns each unique combination of color and size.

Filter results with the WHERE clause

Most queries for application development or reporting involve filtering the data to match specified criteria. You typically apply filtering criteria as a predicate in a WHERE clause of a query.

In Azure Data Studio, replace the existing query with the following code:

 SELECT Name, Color, Size
 FROM SalesLT.Product
 WHERE ProductModelID = 6
 ORDER BY Name;

Run the query and review the results, which contain the Name, Color, and Size for each product with a ProductModelID value of 6 (this is the ID for the HL Road Frame product model, of which there are multiple variants).

Replace the query with the following code, which uses the not equal (<>) operator, and run it.

 SELECT Name, Color, Size
 FROM SalesLT.Product
 WHERE ProductModelID <> 6
 ORDER BY Name;

Review the results, noting that they contain all products with a ProductModelID other than 6.

Replace the query with the following code, and run it.

 SELECT Name, ListPrice
 FROM SalesLT.Product
 WHERE ListPrice > 1000.00
 ORDER BY ListPrice;

Review the results, noting that they contain all products with a ListPrice greater than 1000.00.

Modify the query as follows, and run it.

 SELECT Name, ListPrice
 FROM SalesLT.Product
 WHERE Name LIKE 'HL Road Frame %';

Review the results, noting that the LIKE operator enables you to match string patterns. The % character in the predicate is a wildcard for one or more characters, so the query returns all rows where the Name is HL Road Frame followed by any string.

The LIKE operator can be used to define complex pattern matches based on regular expressions, which can be useful when dealing with string data that follows a predictable pattern.

Modify the query as follows, and run it.

 SELECT Name, ListPrice
 FROM SalesLT.Product
 WHERE ProductNumber LIKE 'FR-_[0-9][0-9]_-[0-9][0-9]';

Review the results. This time the results include products with a ProductNumber that matches patterns similar to FR-xNNx-NN (in which x is a letter and N is a numeral).

Tip: To learn more about pattern-matching with the LIKE operator, see the Transact-SQL documentation.

Modify the query as follows, and run it.

SELECT Name, ListPrice
FROM SalesLT.Product
WHERE SellEndDate IS NOT NULL;

Note that to filter based on NULL values you must use IS NULL (or IS NOT NULL) you cannot compare a NULL value using the = operator.
Now try the following query, which uses the BETWEEN operator to define a filter based on values within a defined range.
```
SELECT Name
FROM SalesLT.Product
WHERE SellEndDate BETWEEN '2006/1/1' AND '2006/12/31';
```
Review the results, which contain products that the company stopped selling in 2006.
Run the following query, which retrieves products with a ProductCategoryID value that is in a specified list.
```
SELECT ProductCategoryID, Name, ListPrice
FROM SalesLT.Product
WHERE ProductCategoryID IN (5,6,7);
```

Now try the following query, which uses the AND operator to combine two criteria.

SELECT ProductCategoryID, Name, ListPrice, SellEndDate
FROM SalesLT.Product
WHERE ProductCategoryID IN (5,6,7) AND SellEndDate IS NULL;

Try the following query, which filters the results to include rows that match one (or both) of two criteria.

SELECT Name, ProductCategoryID, ProductNumber
FROM SalesLT.Product
WHERE ProductNumber LIKE 'FR%' OR ProductCategoryID IN (5,6,7);

Challenges

Now that you’ve seen some examples of filtering and sorting data, it’s your chance to put what you’ve learned into practice.

Tip: Try to determine the appropriate queries for yourself. If you get stuck, suggested answers are provided at the end of this lab.

Challenge 1: Retrieve data for transportation reports

The logistics manager at Adventure Works has asked you to generate some reports containing details of the company’s customers to help to reduce transportation costs.

Retrieve a list of cities
- Initially, you need to produce a list of all of you customers’ locations. Write a Transact-SQL query that queries the SalesLT.Address table and retrieves the values for City and StateProvince, removing duplicates and sorted in ascending order of city.
Retrieve the heaviest products
- Transportation costs are increasing and you need to identify the heaviest products. Retrieve the names of the top ten percent of products by weight.

Challenge 2: Retrieve product data

The Production Manager at Adventure Works would like you to create some reports listing details of the products that you sell.

Retrieve product details for product model 1
- Initially, you need to find the names, colors, and sizes of the products with a product model ID 1.
Filter products by color and size
- Retrieve the product number and name of the products that have a color of black, red, or white and a size of S or M.
Filter products by product number
- Retrieve the product number, name, and list price of products whose product number begins BK-
Retrieve specific products by product number
- Modify your previous query to retrieve the product number, name, and list price of products whose product number begins BK- followed by any character other than R, and ends with a - followed by any two numerals.

Challenge Solutions

This section contains suggested solutions for the challenge queries.

Challenge 1

Retrieve a list of cities:

 SELECT DISTINCT City, StateProvince
 FROM SalesLT.Address
 ORDFER BY City

Retrieve the heaviest products:

 SELECT TOP (10) PERCENT WITH TIES Name
 FROM SalesLT.Product
 ORDER BY Weight DESC;

Challenge 2

Retrieve product details for product model 1:

 SELECT Name, Color, Size
 FROM SalesLT.Product
 WHERE ProductModelID = 1;

Filter products by color and size:

 SELECT ProductNumber, Name
 FROM SalesLT.Product
 WHERE Color IN ('Black','Red','White') AND Size IN ('S','M');

Filter products by product number:

 SELECT ProductNumber, Name, ListPrice
 FROM SalesLT.Product
 WHERE ProductNumber LIKE 'BK-%';

Retrieve specific products by product number:

 SELECT ProductNumber, Name, ListPrice
 FROM SalesLT.Product
 WHERE ProductNumber LIKE 'BK-[^R]%-[0-9][0-9]';