It is recommended that the table in a relational database, should have one of the columns applied with primary key constraint. Accordingly, Peewee Model class can also specify field attribute with primary-key argument set to True. However, if model class doesn’t have any primary key, Peewee automatically creates one with the name “id”. Note that the User model defined above doesn’t have any field explicitly defined as primary key. Hence, the mapped User table in our database has an id field.

To define an auto-incrementing integer primary key, use AutoField object as one attribute in the model.

class User (Model):
   user_id=AutoField()
   name=TextField()
   age=IntegerField()
   class Meta:
      database=db
      db_table=''User''

This will translate into following CREATE TABLE query −

CREATE TABLE User (
   user_id INTEGER NOT NULL
   PRIMARY KEY,
   name TEXT NOT NULL,
   age INTEGER NOT NULL
);

You can also assign any non-integer field as a primary key by setting primary_key parameter to True. Let us say we want to store certain alphanumeric value as user_id.

class User (Model):
   user_id=TextField(primary_key=True)
   name=TextField()
   age=IntegerField()
   class Meta:
      database=db
      db_table=''User''

However, when model contains non-integer field as primary key, the save() method of model instance doesn’t cause database driver to generate new ID automatically, hence we need to pass force_insert=True parameter. However, note that the create() method implicitly specifies force_insert parameter.

User.create(user_id=''A001'',name="Rajesh", age=21)
b=User(user_id=''A002'',name="Amar", age=20)
b.save(force_insert=True)

The save() method also updates an existing row in the table, at which time, force_insert primary is not necessary, as ID with unique primary key is already existing.

Peewee allows feature of defining composite primary key. Object of CompositeKey class is defined as primary key in Meta class. In following example, a composite key consisting of name and city fields of User model has been assigned as composite key.

class User (Model):
   name=TextField()
   city=TextField()
   age=IntegerField()
   class Meta:
      database=db
      db_table=''User''
      primary_key=CompositeKey(''name'', ''city'')

This model translates in the following CREATE TABLE query.

CREATE TABLE User (
   name TEXT NOT NULL,
   city TEXT NOT NULL,
   age INTEGER NOT NULL,
   PRIMARY KEY (
      name,
      city
   )
);

If you wish, the table should not have a primary key, then specify primary_key=False in model’s Meta class.