Modify the columns from your data source

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When working with rows of data in Power Apps, functions like Filter and Search help refine the rows themselves. However, there are scenarios where you need to manipulate the columns within those rows without altering the original data source.

Imagine creating a shopping cart app where you want to keep track of selected items. In such cases, having a temporary column solely within Power Apps, without affecting the original data source, becomes crucial.

Thankfully, Power Apps provides a set of functions tailored for this purpose. These functions allow you to modify columns within your app environment, affecting how the data is handled or presented without making any changes to the underlying data source. This ensures that your alterations, such as tracking selected items in a shopping cart scenario, are confined within the app and don't affect the actual data source. Those functions are:

• AddColumns

• DropColumns

• RenameColumns

• ShowColumns

AddColumns

The AddColumns function adds a column to a table, and a formula defines the values in that column. Existing columns remain unmodified.

For the previous example of a shopping cart app, you would use the AddColumns function to add a column for tracking if the user selected the column. You would do this by setting the following formula for the OnSelect property for a Button control.

ClearCollect(collectDigitalAssets, AddColumns(YourDataSource,"UserSelected", false))

When this button is selected, the formula creates a collection named collectDigitalAssets that has all of the rows from YourDataSource and adds the column, "UserSelected". The column value is false for all of the rows.

Now in your Gallery control, set the items property to the following.

collectDigitalAssets

In the Gallery control, you would have access to a column named UserSelected and the value would be false. You could then add a button into your Gallery that OnSelect would patch the column to true.

Patch(collectDigitalAssets, ThisItem, {UserSelected: true})

Now in the collectDigitalAssets collection you're tracking the rows the user selected in your app without modifying the columns in your data source.

DropColumns

The DropColumns function works the opposite of AddColumns. The function is used to remove columns from the table within Power Apps. This function is used when you want to create a collection within Power Apps that has several columns for app functionality. Because these columns are added only in the collection for app functionality and not submitted to the data source, the DropColumns function is needed to remove the column upon submission to the data source.

For example, you create a collection name collectTimeTracking to use in a time tracking application. The collection has five columns: Name, HoursWorked, DateWorked, LastScreen, and Status. The columns Name, HoursWorked, and DateWorked track the data to save to YourDataSource based on hours an employee worked. The columns LastScreen and Status store data to provide app functionality while the user is using the app.

When the user is done, one way to save the information back to a data source is to use the Collect function. If the columns match between the data source, the Collect function writes all of the rows to your collection. In this example, Name, HoursWorked, and DateWorked are the only columns in the data source. LastScreen and Status don't exist in the data source and don't need to be saved. You can use DropColumns to send just the appropriate columns to the data source.

Collect(YourDataSource, DropColumns(collectTimeTracking, "LastScreen","Status"))

This function will write the contents of the collection, collectTimeTracking, to the data source, YourDataSource, after dropping the columns LastScreen and Status. Note,DropColumns didn't alter your collection collectTimeTracking. The LastScreen and Status columns are still available within the collection.

RenameColumns

Use the RenameColumns function when you need to manipulate the name of the column within your app but not within your data source. A common use is when the data source, which you can't edit, has difficult to reference column name or the column name uses reserved words, like "Date."

You can use the function when storing data into a collection. The Collect function can take the contents of your data source and store them into a collection.

Collect(collectProjectData, ProjectDataSource)

This formula would create a collection named collectProjectData that stores all of the rows of data from the data source, ProjectDataSource. If the data source has a column named Date, you might find it easier to work in Power Apps by renaming that column to ProjectDate. You can do that by using the following formula instead of the previous example.

Collect(collectProjectData, RenameColumns(ProjectDataSource, "Date","ProjectDate"))

You have the same rows. Now, instead of the column being named Date, it's now named ProjectDate within your collection. This gives you the flexibility to name columns to something that is less confusing to work with in the app.

ShowColumns

ShowColumns is used to display one or more columns from your data source. Use this with controls where you only want a single column returned. A common example is the dropdown control.

With the dropdown control, it's common to use a data source, such as a Microsoft Dataverse table, to provide the options. When you set the items property to a data source, Power Apps chooses which column, if you have multiple, to display. You can use the ShowColumns function to select the column that you want to display.

If you wanted to use a data source named Customers to display customer names from the CustomerName column. You would use the following formula in the Items property of the Dropdown control.

ShowColumns(Customers, "CustomerName")

With this formula, the Dropdown column displays the values from the CustomerName column.

ShowColumns can also return more than one column. The Dropdown control only displays the first column, but you have access to all the retrieved columns. The following example shows how to add the ID column to your Dropdown control.

ShowColumns(Customers, "CustomerName", "ID")

The dropdown only displays the value from CustomerName column in the Dropdown control, but with this formula, you now have access to the value of the ID column. Add a Label control to the screen and set the Text value to the following. If your dropdown isn't named Dropdown1, edit the formula accordingly.

Dropdown1.Selected.ID

The formula returns the value from the ID column for the selected row in your Dropdown control.