What do I need to consider when editing my Target Data Extension?

When editing a Target Data Extension, there are some points that need to be considered.

Removing and re-adding the same field in the same update of my Target Data Extension

Important Note: Something to consider is checking if it is the field that is being used in your subscriber relationship.

When you are trying to remove and re-add a field, you might encounter the below messages. 

1. You will be encountering the below warning message in case you are trying to remove or delete a field that is being used in the subscriber relationship.

Normally, this can be removed, however, once done, DESelect will automatically change the field being used in the subscriber relationship to the next field listed on your Target Data Extension.

2. In case you proceed with deleting the field and decided to add it again on your Target Data Extension, you will be encountering the below warning message.

This is because the field name of the priorly deleted field used in your subscriber relationship (since the Target Data Extension is not being updated yet) will have the same field name as what you are adding.

Thus, you can provide a new name for the field that you are adding and you can proceed as you normally would.

Recommendation

Our recommendation will be to remove the field and add it again in two update steps:

1. Remove the field and click on "Update Target Data Extension"
2. Edit the Target Data Extension again, and add the field
3. Click on "Update Target Data Extension"

Modifying a field as a Primary Key or Nullable

Important Note: Something to consider is the fact that the Primary Key and Nullable properties of the fields have already been set upon the creation of the Target Data Extension.

When you are trying to edit the Primary Key and Nullable properties of your fields, you might find that they are grayed out and cannot be edited.

In case you want to edit those fields' properties, you can delete the current Target Data Extension field and re-add it. This way, DESelect will be deleting the field together with the priorly set properties and adding a new one where you can provide the correct properties.

Adding a field set as Primary Key or Not nullable field to an existing Target Data Extension

Important Note: Something to consider is that the Target Data Extension already has existing records on it.

If the Target Data Extension has records on it and you try to add new columns that are non-nullable (like Primary Keys, or regular fields without the "Nullable" checkbox marked), the update of the Data Extension will result in an error, because adding the column will make the existing records invalid (as they don't have a value for the newly added column)

The workaround consists in empty the Target Data Extension from the Email Studio (opening the Data Extension > Records > Clear Data), and trying to perform the modification again.