Creating a Basic Query in LightSwitch
This lesson shows how to create a LightSwitch query to return a subset of customer names.
Create a Query
A query returns data that meets a set of criteria. For example, a query might return a list of orders for customers who are located in the United States or Canada. In this example, orders are the data, and customers located in United States or Canada is the criterion.
Note
This lesson builds on the My First Application project that's developed in the Working with Data in LightSwitch lessons and modified in the Creating Screens in LightSwitch lessons. If you've completed the earlier lessons, open the project now; otherwise, complete those prerequisite lessons, and then return to this lesson.
To create a query
In Solution Explorer, open the shortcut menu for the BrowseOrders.lsml node, and then choose Open.
In the left pane of the Screen Designer, choose the Orders node, and then choose the Edit Query link.
In the Query Designer, choose the Add Filter link.
A filter condition is added to the Filter section. Several lists and a text box appear next to the filter condition.
In the first list, choose Where.
In the second list, choose ShipCountry.
In the third list, choose = (equals).
In the fourth list, choose Literal.
In the text box, enter USA, and then choose the Add Filter link again.
In the first list, choose Or.
In the second list, choose ShipCountry.
In the third list, choose = (equals).
In the fourth list, choose Literal.
In the text box, enter Canada.
This query will return all records from Orders where the value of the ShipCountry field equals either the literal value "USA" or the literal value "Canada".
Choose the Add Sort link.
In the first list, choose ShipCity.
The results will be sorted by the city name in ascending (A-Z) order.
.png "The BrowseOrders query")
On the toolbar, choose the Back to BrowseOrders link to return to the Screen Designer.
In the center pane, choose the Table Row | rows node, and then open the Add list and choose ShipCountry.
Open the Add list, and then choose ShipCity.
Run the application, and open the BrowseOrders screen.
Notice that only orders for customers in the USA or Canada appear and that the results are sorted by city name.
Closer Look
This lesson showed how to create a query that returns a subset of customers. The filter section of the query specified a condition, and the sort section specified how to order the results. Translated to natural language, the query says, "Give me a list of all orders that are being shipped to customers in the USA or Canada, sorted by city name."
In the first filter list, you could choose either Where or WhereNot. If you change the clause to WhereNot, the query would return orders for customers from everywhere except the USA or Canada.
The third filter list contains operators that you can apply to the query. For example, if you had chosen a numeric field in the second list, you could choose > (is greater than) to return only those records that exceeded a specified amount.
The fourth filter list contains three choices: Literal, Property, and Parameter. As demonstrated in this lesson, Literal means that the criterion is a value in the database. If you had chosen Property, a list of the fields in the Orders entity would have appeared so that you could filter results by property. For example, you could return all orders where the ShipName matches the Customer. The Parameter option is described in the Creating a Parameterized Query in LightSwitch lesson.
The sort section of a query determines the order in which the results appear on a screen in the running application.
Next Steps
In the next lesson, you’ll learn how to create a screen that's based on a query.
Next lesson: Creating a LightSwitch Screen Based on a Query
See Also
Tasks
How to: Add, Remove, and Modify a Query
How to: Extend a Query by Using Code