Django学习小记4-学员数据库管理②

上一篇 Django学习小记3-学员管理数据库① 我们提到的是最基本的单表操作。实际还有一对多、多对多的案例。

多表涉及到连表操作。

理解：Form表单提交，页面会刷新。

1. 查看

mysql> SELECT * FROM student LEFT JOIN class ON student.`class_ID`=class.`id`;
+----+-----------+----------+------+-----------------+
| id | name      | class_ID | id   | title           |
+----+-----------+----------+------+-----------------+
|  1 | 张英杰    |        9 |    9 | 全栈12期1222    |
+----+-----------+----------+------+-----------------+
1 row in set (0.00 sec)

mysql> SELECT student.id,student.name,class.title FROM student LEFT JOIN class ON student.`class_ID`=cllass.`id`;
+----+-----------+-----------------+
| id | name | title |
+----+-----------+-----------------+
| 1 | 张英杰 | 全栈12期1222 |
+----+-----------+-----------------+
1 row in set (0.00 sec)

所以在数据库语句就可以替换成：

#展示学生
def students(request):
    import pymysql
    conn = pymysql.connect(host='10.0.4.x', port=3306, user='root', passwd='123@#123', db='oldboys',charset='utf8')
    cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
    cursor.execute("SELECT student.id,student.name,class.title FROM student LEFT JOIN class ON student.`class_ID`=class.`id`")
    student_list = cursor.fetchall()
    cursor.close()
    conn.close()

    return render(request,'students.html',{'student_list':student_list})

2.添加

在页面让用户添加所属班级时，可以设置一个下拉框，用<select><option>标签实现：add_student.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>添加学生</title>
</head>
<body>
    <h1>增加学生</h1>
    <form method="POST" action="/add_student/">
        <p>学生姓名<input type="text" name="name"/></p>
        <p>所属班级：
            <select name="class_id">
                {% for row in class_list %}
                    <option value="{{ row.id }}">{{ row.title }}</option>>
                {% endfor %}
            </select>
        </p>
        <input type="submit" value="提交">
    </form>
</body>
</html>

注意：在select标签加入了class_id属性，这样提交的学生name作为key，class_id作为value来提交。

views.py里添加add_student函数：

...
#添加学生，下拉框
def add_student(request):
    if request.method == "GET":
　　　　　#由数据库提取班级名称填充value到add_student.html的下拉框
        import pymysql
        conn = pymysql.connect(host='10.0.4.x', port=3306, user='root', passwd='123!@#123', db='oldboys',charset='utf8')
        cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
        cursor.execute("select id,title from class")
        class_list = cursor.fetchall()
        cursor.close()
        conn.close()
        return render(request,'add_student.html',{'class_list':class_list})
    else:
        name = request.POST.get('name')
        class_id = request.POST.get('class_id')
　　　　 #提交至数据库
        import pymysql
        conn = pymysql.connect(host='10.0.4.x', port=3306, user='root', passwd='123!@#123', db='oldboys',charset='utf8')
        cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
        cursor.execute("insert into student(name,class_id) values(%s,%s)",[name,class_id])
        conn.commit()
        cursor.close()
        conn.close()
        return redirect('/students/')

其实这样每次都去操作数据库太繁琐了，可以把他们封装在utils目录下起名sqlheper.py

sqlheper.py

import pymysql

#fetchall
def get_list(sql,args):
    conn = pymysql.connect(host='10.0.4.x', port=3306, user='root', passwd='123!@#123', db='oldboys',charset='utf8')
    cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
    cursor.execute(sql,args)
    result = cursor.fetchall()
    cursor.close()
    conn.close()
    return result

#fetchone
def get_one(sql,args):
    conn = pymysql.connect(host='10.0.4.x', port=3306, user='root', passwd='123!@#123', db='oldboys',charset='utf8')
    cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
    cursor.execute(sql,args)
    result = cursor.fetchone()
    cursor.close()
    conn.close()
    return result

#commit
def modify(sql,args):
    conn = pymysql.connect(host='10.0.4.x', port=3306, user='root', passwd='123!@#123', db='oldboys',charset='utf8')
    cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
    cursor.execute(sql,args)
    conn.commit()
    cursor.close()
    conn.close()

Ajax (jQuery)

“页面不刷新的情况下偷偷提交数据”