Model and Model Fields

• SQL : Programming language for managing data in RDBMS(Relational Database Management System).
• Kinds of SQL : PostgreSQL, MySQL, MariaDB, etc.
• Django model only supports RDBMS
• Create/Run SQL with Django model(ORM : Object Relational Mapping)
• With Django ORM, you don’t need to write SQL and the ORM does it itself
  • ORM does CRUD(Create/Read/Update/Delete)

• BUT!! You should know SQL for checking what ORM does.

• Python class and Database Table
  • Model : DB Table
  • Model Instance : 1 Row of DB Table
  • e.g. blog application, Post Model : blog_post DB Table
    e.g. blog application, Comment Model : blog_comment DB Table
    
• The table below is DB Table and total DB Table is DB.

• A djnago project has only one DB and many DB Tables.
  • Workbook (Excel) = DB (Django DB)
  • Worksheet = DB Table
  • Row(1,2,3,4, …) = Instance
  • Column(A,B,C,D, …) = Field

We should designate Field Type. Maybe you can select options below.

• AutoField
• BooleanField
• CharField
• DateTimeField
• FileField
• ImageField
• TextField
• IntegerField

You can use Relationship Type. + ForeignKey + ManyToManyField + OneToOneField

Field Options you can use in generally + null : whether to allow NULL value (Default : False) + unique : uniqueness + blank : whether to allow empty value (Default : False) + validators : designate function to check validations + verbose_name : specify field name + DataTimeField(auto_now_add = True) for created_at + DataTimeFiled(auto_now = True) for updated_at + …

e.g.

Class Post(models.Model):
    title = models.CharField(max_length = 100,
                             verbose_name = "PostTitle",
                             help_text = "Enter the Post title within 100 characters")
    
    content = models.Textfield()
    tags = models.CharField(max_length = 100,
                            blank = True)
    lnglat = models.CharField(max_length = 50,
                              blank = True,
                              validators = [lnglat_validator],
                              help_text = "Enter the format with langitude/latitude")
    created_at = models.DateTimeField(auto_now_add = True)
    updated_at = models.DateTimeField(auto_now = True)