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In QuickBase we call what you refer to as a dependency, a relationship. A relationship always involves two tables.
In the example above one of the tables would be a table of users. The users table would have a field for email address and a field for phone number. The users table, in this relationship, is the master table.
The other table would be the tasks table. The tasks table, in this relationship, is the details table. (To learn more, please see our About Relationships help topic.)
You can enhance this relationship with "lookup fields." Lookup fields draw additional values from the Master (users) into the details table. In this case, you'd just create lookup fields for the email address and phone number fields. (Read how to add lookup fields to a relationship in this help topic.)
Then when you add new task and select a user related master record), their email address and phone number automatically populates.