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Go to the official document first!

Filter (* * kwargs)

Returns a new query set that contains objects that match the given lookup parameters.

To put it simply, return a collection of queries made up of objects

Get (* * kwargs)

Returns an object that matches the given lookup parameter in the format described in the field lookup.

Examples

For example, there is an Order class in Model that contains an id field, and enter an id whose id is the 2019 field.

1.get () method

Orders = Orders.objects.get (id=20190003) print (order)

Check what orders is first, and the result is

Orders object

According to the official document, he is an object, yes, you can directly use a point operation to take the value of the field.

Print (order.id)

The result is 20190003.

The get method of 1. 1 django takes a matching result from the database and returns an object that reports an error if the record does not exist.

For example, there is a record in my database, and the value of the recorded name is "Lao Wang python". I use student= Student.objects.get (name=' Lao Wang python') to return a record object, which can be viewed through student.__dict__. It returns the form of a dictionary. {'key':valeus}, key is the name of the field, and values is the content of the value. If I use the get method to query a record that does not exist in the database, the program will report an error. For example: student = Student.objects.get (name=' Lao Wang').

1.2 if you use the get of django to get the data of the associated table, and if the data of the key table is more than 2 items, it will also report an error.

2.filter () method

Orders = Orders.objects.filter (id=20190003) print (order)

Check what orders is first.

I think the previous QuerySet tells us that this is a query set, and the real content of the query set is the contents of the list [], indicating the scope of the query set. The same goes for Orders in []. At this point, we find that what is in [] is what the get () method gets, so we just need to take order [0] and print order [0] to see it.

Orders object

Therefore, order [0] .id. You can get 20190003.

Note: if the filter query returns more than one result, the result is

It essentially looks like a list.

Add: the filter method of 2.1django gets matching results from the database and returns a list of objects. If the record does not exist, it returns [].

For example, there is a record in my database. If the value of name recorded is Lao Wang python, I use student = Student.objects.filter (name=' Lao Wang python'). The student returned by it is a list of objects. You can see that the result of student [0] is the same as the student returned by get above.

2.2 if you use django's filter to get the data of the associated table, no matter how many records there are in the associated table, it will not report an error.

In addition, I see from other materials that filter seems to have the function of caching data, querying the database for the first time and generating the cache, and the next time you call the filter method, you will directly get the cached data, and the get method will query the database directly every time. I don't know if this is correct.

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