81 lines
2.3 KiB
Markdown
81 lines
2.3 KiB
Markdown
# Read/ Load data from database
|
|
|
|
* `get(**kwargs): -> Model`
|
|
* `get_or_create(**kwargs) -> Model`
|
|
* `first(): -> Model`
|
|
* `all(**kwargs) -> List[Optional[Model]]`
|
|
* `Model.load() method`
|
|
|
|
## get
|
|
|
|
`get(**kwargs): -> Model`
|
|
|
|
Get's the first row from the db meeting the criteria set by kwargs.
|
|
|
|
If no criteria set it will return the last row in db sorted by pk.
|
|
|
|
Passing a criteria is actually calling filter(**kwargs) method described below.
|
|
|
|
```python
|
|
track = await Track.objects.get(name='The Bird')
|
|
# note that above is equivalent to await Track.objects.filter(name='The Bird').get()
|
|
track2 = track = await Track.objects.get()
|
|
track == track2 # True since it's the only row in db in our example
|
|
```
|
|
|
|
!!!warning If no row meets the criteria `NoMatch` exception is raised.
|
|
|
|
If there are multiple rows meeting the criteria the `MultipleMatches` exception is raised.
|
|
|
|
## get_or_create
|
|
|
|
`get_or_create(**kwargs) -> Model`
|
|
|
|
Combination of create and get methods.
|
|
|
|
Tries to get a row meeting the criteria and if `NoMatch` exception is raised it creates
|
|
a new one with given kwargs.
|
|
|
|
```python
|
|
album = await Album.objects.get_or_create(name='The Cat')
|
|
# object is created as it does not exist
|
|
album2 = await Album.objects.get_or_create(name='The Cat')
|
|
assert album == album2
|
|
# return True as the same db row is returned
|
|
```
|
|
|
|
!!!warning Despite being a equivalent row from database the `album` and `album2` in
|
|
example above are 2 different python objects!
|
|
Updating one of them will not refresh the second one until you excplicitly load() the
|
|
fresh data from db.
|
|
|
|
!!!note Note that if you want to create a new object you either have to pass pk column
|
|
value or pk column has to be set as autoincrement
|
|
|
|
## first
|
|
|
|
`first(): -> Model`
|
|
|
|
Gets the first row from the db ordered by primary key column ascending.
|
|
|
|
## all
|
|
|
|
`all(**kwargs) -> List[Optional["Model"]]`
|
|
|
|
Returns all rows from a database for given model for set filter options.
|
|
|
|
Passing kwargs is a shortcut and equals to calling `filter(**kwrags).all()`.
|
|
|
|
If there are no rows meeting the criteria an empty list is returned.
|
|
|
|
```python
|
|
tracks = await Track.objects.select_related("album").all(title='Sample')
|
|
# will return a list of all Tracks with title Sample
|
|
|
|
tracks = await Track.objects.all()
|
|
# will return a list of all Tracks in database
|
|
|
|
```
|
|
|
|
## Model method
|