问题
I have a MySQL database unfortunately used with Django 1.4.1. Distinct function is only working for POSTGRESQL if i get it right.
I have to make a distinct query consist of multiple values while only distinct one,
Like; This one works for POSTGRE but not with MYSQL, I get the following error;
DISTINCT ON fields is not supported by this database backend
staff = Staff.objects.order_by('person__full_name').distinct('person__full_name')
Then I tried
staff = Staff.objects.values('person__full_name','staff_job_categories').distinct().order_by('person__full_name')
But I do not get distinct values because i get also the staff job categories. But when I dont contain it I could not get it as array.
Any idea ?
回答1:
.distinct([*fields]) only works in PostgresSQL.
From distinct documentation
Here's the difference. For a normal distinct() call, the database compares each field in each row when determining which rows are distinct. For a distinct() call with specified field names, the database will only compare the specified field names.
As stated all fields in a record are checked. Mostly likely in your case you are getting records with different field values (more likely a case if you are queries multiple tables ManyToMany or ForeignKey relations).
For consolidating as array you can refer your earlier question Django Query distinct values works but i cant use the query result
回答2:
names = Staff.objects.order_by('person__full_name').values('person__full_name').distinct()
will give you distinct full names, and you can do a similar thing to get distinct job categories.
These will give you lists of values, not objects themselves, but if I interpret your question correctly then I think these will give you what you want.
来源：https://stackoverflow.com/questions/12402923/django-mysql-distinct-query-for-getting-multiple-values