Updating multiple tables in pl sql
The above example will return the last item first, then the penultimate item and so on. If you order by fields from a related model, those fields will be added to the selected columns and they may make otherwise duplicate rows appear to be distinct.
Since the extra columns don’t appear in the returned results (they are only there to support ordering), it sometimes looks like non-distinct results are being returned.
To put it simply: if you need to ask, you don’t need to use it. An expression may be a simple value, a reference to a field on the model (or any related models), or an aggregate expression (averages, sums, etc.) that has been computed over the objects that are related to the objects in the that is returned.
The aggregation functions that are provided by Django are described in Aggregation Functions below.
Only aggregate expressions that reference a single field can be anonymous arguments. For example, if you were manipulating a list of blogs, you may want to determine how many entries have been made in each blog: queries may be expensive and slow, depending on the database backend you’re using.
To order by a field in a different model, use the same syntax as when you are querying across model relations.
A particular ordering is guaranteed only when ordering by a set of fields that uniquely identify each object in the results.
Pickles should not be used as part of a long-term archival strategy.
This means that when you unpickle a attribute is an opaque object.
It represents the internals of the query construction and is not part of the public API.
Annotations specified using keyword arguments will use the keyword as the alias for the annotation.
Anonymous arguments will have an alias generated for them based upon the name of the aggregate function and the model field that is being aggregated.