在Django中如何执行原生SQL查询详解

from myapp.models import Person

# 基本查询
people = Person.objects.raw('SELECT * FROM myapp_person WHERE age > %s', [18])

# 遍历结果
for person in people:
    print(person.name, person.age)

# 带参数的查询
people = Person.objects.raw(
    'SELECT * FROM myapp_person WHERE age BETWEEN %s AND %s',
    [20, 30]
)

from django.db import connection

def my_custom_sql():
    with connection.cursor() as cursor:
        # 执行查询
        cursor.execute("SELECT * FROM myapp_person WHERE age > %s", [25])
        
        # 获取所有结果
        rows = cursor.fetchall()
        
        # 或者逐行获取
        # row = cursor.fetchone()
        # rows = cursor.fetchmany(size=10)
    
    return rows

from django.db import connection

def dictfetchall(cursor):
    """将游标结果转换为字典列表"""
    columns = [col[0] for col in cursor.description]
    return [
        dict(zip(columns, row))
        for row in cursor.fetchall()
    ]

def my_custom_sql():
    with connection.cursor() as cursor:
        cursor.execute("SELECT id, name, age FROM myapp_person")
        results = dictfetchall(cursor)
    return results

from django.db import connections

def query_multiple_dbs():
    # 使用默认数据库
    with connections['default'].cursor() as cursor:
        cursor.execute("SELECT * FROM table1")
        # 处理结果
    
    # 使用其他数据库
    with connections['other_db'].cursor() as cursor:
        cursor.execute("SELECT * FROM table2")
        # 处理结果

from django.db import connection

def update_data():
    with connection.cursor() as cursor:
        # INSERT
        cursor.execute(
            "INSERT INTO myapp_person (name, age) VALUES (%s, %s)",
            ['John', 30]
        )
        
        # UPDATE
        cursor.execute(
            "UPDATE myapp_person SET age = %s WHERE name = %s",
            [31, 'John']
        )
        
        # DELETE
        cursor.execute(
            "DELETE FROM myapp_person WHERE age < %s",
            [18]
        )

from django.db import transaction, connection

@transaction.atomic
def complex_operation():
    with connection.cursor() as cursor:
        try:
            # 一系列SQL操作
            cursor.execute("UPDATE accounts SET balance = balance - %s", [100])
            cursor.execute("UPDATE accounts SET balance = balance + %s", [100])
        except Exception as e:
            # 出错时会自动回滚
            print(f"Error: {e}")

from django.db import connection

def execute_query(query, params=None, return_dict=True):
    """
    执行SQL查询的通用函数
    """
    with connection.cursor() as cursor:
        cursor.execute(query, params or [])
        
        if query.strip().upper().startswith('SELECT'):
            if return_dict:
                columns = [col[0] for col in cursor.description]
                return [dict(zip(columns, row)) for row in cursor.fetchall()]
            else:
                return cursor.fetchall()
        else:
            # 对于非SELECT查询，返回受影响的行数
            return cursor.rowcount

# 使用示例
results = execute_query(
    "SELECT name, age FROM myapp_person WHERE age > %s",
    [25]
)