Python Study notes Week 20th

Directory:

　　First, ORM

1. Supplementary Enquiry

Content:

First, ORM

1, Query Supplement:

1, models. USR.objects.all (). VALUES (' id ', ' name ')

This statement is equivalent to the Select Id,name from USER in the SQL statement, which means that the values of a few columns can be taken separately, and the obtained value is still queryset, but the inner element becomes a dictionary

2, models. USR.objects.all (). Value_list (' id ', ' name ')

Represents a value that can be taken separately from a few columns, and the obtained value is still queryset, but the inner element becomes a tuple

3, models. USR.objects.filter (id=1). First ()

Represents a single object, if the fetch is not returned to none

4, models. USR.objects.filter (nid__gt=0). VALUES (' nid ', ' hostname ', ' b_id ', ' b__caption ')

Here are two points to note:

1. Nid is followed by a __gt with two underscores, also less than, greater than or equal to less than or equal to (__lt __gte __lte) These are double underlines

2, in the values of the need to cross-table value, the same need double underline, such as b__caption, but b_id is a single underline, because it is only in the user table does not have a cross-table value, where the common cross-table value of "." is not valid, you must use "__"

Python Study notes Week 20th