Teach you how to execute native SQL with Django

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Preface

Hey, friends, how to play this time, how to use Django to execute native SQL.

We all know that Python's handle in the web world-Django, can be described as a unified integration, a variety of plug-ins, forms components, model models, Admin backend, etc., I will give a special article later. , Anyway, it is a word, NB.

This time, let’s learn how to execute native statements in Django.

Cause

When using Django, under normal circumstances, we use Django's own model query is no problem, and can basically meet 80% of the problems

But, but, don’t you want 20%? It’s definitely not good, children only make a choice

There are three ways to execute native SQL in Django

extra
raw
django connection

Under normal circumstances, the above three methods

Table Structure

file:django_project/app01/models

class Book(models.Model):
    title = models.CharField(verbose_name="书名", max_length=32)
    describe = models.TextField(verbose_name="描述")
    author = models.CharField(verbose_name="作者", max_length=32)
    publisher = models.CharField(verbose_name="出版社", max_length=32)
    publisher_date = models.DateField(verbose_name="publisher")

Is a very simple book list

Enter some data through admin to test use

extra way

It is strongly recommended, no need to learn, no use

raw way

Compared with extra, this is more useful.

The syntax is as follows

models.表名.objecs.raw(sql)
models.表名.objecs.raw(sql,[参数1,参数2])

Note: If there are no parameters, just write the sql statement. If there are parameters, you need to use a list later, as shown in the figure

For example

Returned still one Book object

The true native sql way

The above is actually some binding with django's model. But I mean, I just want native SQL, don't bind it to anything.

Here to talk about it, do not use pymysql to execute native sql in django, some strange problems will occur. Be sure to import and from django.db import connectionexecute sql. code show as below:

from django.db import connection
def book_list(request):
    # 真正的原生sql,
    cursor = connection.cursor()
    print(type(cursor))
    cursor.execute("select * from app01_book where id=%s", [1, ])
    raw = cursor.fetchall()
    print(raw)

The returned content is shown in the figure below:

As you can see, what is returned is an array of sets in the list. I was thinking, is there any way to return the queried sql directly into a dictionary? The answer is of course!

Execute native sql and return to dict

I encapsulated the way of executing native sql and directly returning to a dictionary into two functions

One is to query multiple, the code is as follows:

def query_all_dict(sql, params=None):
    '''
    查询所有结果返回字典类型数据
    :param sql:
    :param params:
    :return:
    '''
    with connection.cursor() as cursor:
        if params:
            cursor.execute(sql, params=params)
        else:
            cursor.execute(sql)
        col_names = [desc[0] for desc in cursor.description]
        row = cursor.fetchall()
        rowList = []
        for list in row:
            tMap = dict(zip(col_names, list))
            rowList.append(tMap)
        return rowList

One is to query the other, the code is as follows:

def query_one_dict(sql, params=None):
    """
    查询一个结果返回字典类型数据
    :param sql:
    :param params:
    :return:
    """
    with connection.cursor() as cursor:
        if params:
            cursor.execute(sql, params=params)
        else:
            cursor.execute(sql)
        col_names = [desc[0] for desc in cursor.description]
        row = cursor.fetchone()
        tMap = dict(zip(col_names, row))
        return tMap

The usage is as follows, call the function directly in the view

The returned result is as follows, directly in the list set dictionary format

What to do if the query is conditional, it is actually the same as pymysql

Return result

But there is a problem. In the above query, we clearly know that let only return one value, but it still returns a list set in a dictionary format. It doesn't seem right?

In fact, what I wrote above are two methods. If you are sure, you can query a value and use the query_one_dictmethod.

Above summary

Native sql django performed in 3 ways, extra, raw,from django.db import connection

Which is extrabasically useless, rawmake do, but modelswith binding, the connectionmost flexible, but the default return is [tuple,tuple,tuple,] format

After improvement, the two packaging methods query_all_dict, query_one_dicta plurality of query, a single query, and returns to [dict, dict, dict,]

Suggest

Use only query_all_dict,query_one_dict

Project code

django_exec_sql.zip

Friends who need the complete code of this article can reply to the keyword: native SQL in the background of this official account to get it.

to sum up

The above has been solved in an introductory way and arranged the following how to execute native sql through django.

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