# Django Queryset only and defer

In Django, you can use the `defer()` method on a QuerySet to specify that certain fields should not be retrieved from the database when the QuerySet is evaluated. This can be useful if you have fields in your model that contain large amounts of data and you don't need them for a particular query.

The `exclude()` method is similar to `defer()`, but it works at the row level, while `defer()` works at the attribute level. This means that the arguments passed to `exclude()` are used in the WHERE clause of the generated SQL query, while `defer()` changes the list of fields included in the SELECT clause.

The opposite of `defer()` is `only()`, which allows you to specify that only certain fields should be retrieved from the database.