One to OneΒΆ
A one to one relationship associates one child with one parent and vice-versa. For example, the pay information for an employee may be stored in a different table than the employee. However, one employee can only be paid in one way and each employee must be paid separately.
See also
- One to One
OpenAlchemy documentation for one to one relationships.
- SQLAlchemy One to One
SQLAlchemy documentation for one to one relationships.
The following example defines a one to one relationship between Employee and PayInfo:
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info:
title: Test Schema
description: API to illustrate OpenAlchemy one to one relationship.
version: "0.1"
paths:
/pay_info:
get:
summary: Used to retrieve all payment information.
responses:
200:
description: Return all payment information from the database.
content:
application/json:
schema:
type: array
items:
"$ref": "#/components/schemas/PayInfo"
/employee:
get:
summary: Used to retrieve all employees.
responses:
200:
description: Return all employees from the database.
content:
application/json:
schema:
type: array
items:
"$ref": "#/components/schemas/Employee"
components:
schemas:
PayInfo:
description: Information on how to pay an employee.
type: object
x-tablename: pay_info
properties:
id:
type: integer
description: Unique identifier for the pay information.
example: 0
x-primary-key: true
account_number:
type: string
description: The account number to pay the employee into.
example: David's Account
Employee:
description: Person that works for a company.
type: object
x-tablename: employee
properties:
id:
type: integer
description: Unique identifier for the employee.
example: 0
x-primary-key: true
name:
type: string
description: The name of the employee.
example: David Andersson
pay_info:
allOf:
- "$ref": "#/components/schemas/PayInfo"
- x-backref: employee
x-uselist: false
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The following file uses OpenAlchemy to generate the SQLAlchemy models:
1 2 3 | from open_alchemy import init_yaml
init_yaml("example-spec.yml", models_filename="models_auto.py")
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The SQLAlchemy models generated by OpenAlchemy are equivalent to the following traditional models file:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class PayInfo(Base):
"""Information on how to pay an employee."""
__tablename__ = "pay_info"
id = sa.Column(sa.Integer, primary_key=True)
account_number = sa.Column(sa.String)
class Employee(Base):
"""Person that works for a company."""
__tablename__ = "employee"
id = sa.Column(sa.Integer, primary_key=True)
name = sa.Column(sa.String)
pay_info_id = sa.Column(sa.Integer, sa.ForeignKey("pay_info.id"))
pay_info = sa.orm.relationship("PayInfo", uselist=False)
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OpenAlchemy will generate the following typed models:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 | """Autogenerated SQLAlchemy models based on OpenAlchemy models."""
# pylint: disable=no-member,super-init-not-called,unused-argument
import typing
import sqlalchemy
from sqlalchemy import orm
from open_alchemy import models
Base = models.Base # type: ignore
class PayInfoDict(typing.TypedDict, total=False):
"""TypedDict for properties that are not required."""
id: typing.Optional[int]
account_number: typing.Optional[str]
class TPayInfo(typing.Protocol):
"""
SQLAlchemy model protocol.
Information on how to pay an employee.
Attrs:
id: Unique identifier for the pay information.
account_number: The account number to pay the employee into.
employee: The employee of the PayInfo.
"""
# SQLAlchemy properties
__table__: sqlalchemy.Table
__tablename__: str
query: orm.Query
# Model properties
id: "sqlalchemy.Column[typing.Optional[int]]"
account_number: "sqlalchemy.Column[typing.Optional[str]]"
employee: 'sqlalchemy.Column[typing.Optional["TEmployee"]]'
def __init__(
self,
id: typing.Optional[int] = None,
account_number: typing.Optional[str] = None,
employee: typing.Optional["TEmployee"] = None,
) -> None:
"""
Construct.
Args:
id: Unique identifier for the pay information.
account_number: The account number to pay the employee into.
employee: The employee of the PayInfo.
"""
...
@classmethod
def from_dict(
cls,
id: typing.Optional[int] = None,
account_number: typing.Optional[str] = None,
) -> "TPayInfo":
"""
Construct from a dictionary (eg. a POST payload).
Args:
id: Unique identifier for the pay information.
account_number: The account number to pay the employee into.
employee: The employee of the PayInfo.
Returns:
Model instance based on the dictionary.
"""
...
@classmethod
def from_str(cls, value: str) -> "TPayInfo":
"""
Construct from a JSON string (eg. a POST payload).
Returns:
Model instance based on the JSON string.
"""
...
def to_dict(self) -> PayInfoDict:
"""
Convert to a dictionary (eg. to send back for a GET request).
Returns:
Dictionary based on the model instance.
"""
...
def to_str(self) -> str:
"""
Convert to a JSON string (eg. to send back for a GET request).
Returns:
JSON string based on the model instance.
"""
...
PayInfo: typing.Type[TPayInfo] = models.PayInfo # type: ignore
class EmployeeDict(typing.TypedDict, total=False):
"""TypedDict for properties that are not required."""
id: typing.Optional[int]
name: typing.Optional[str]
pay_info: typing.Optional["PayInfoDict"]
class TEmployee(typing.Protocol):
"""
SQLAlchemy model protocol.
Person that works for a company.
Attrs:
id: Unique identifier for the employee.
name: The name of the employee.
pay_info: The pay_info of the Employee.
"""
# SQLAlchemy properties
__table__: sqlalchemy.Table
__tablename__: str
query: orm.Query
# Model properties
id: "sqlalchemy.Column[typing.Optional[int]]"
name: "sqlalchemy.Column[typing.Optional[str]]"
pay_info: 'sqlalchemy.Column[typing.Optional["TPayInfo"]]'
def __init__(
self,
id: typing.Optional[int] = None,
name: typing.Optional[str] = None,
pay_info: typing.Optional["TPayInfo"] = None,
) -> None:
"""
Construct.
Args:
id: Unique identifier for the employee.
name: The name of the employee.
pay_info: The pay_info of the Employee.
"""
...
@classmethod
def from_dict(
cls,
id: typing.Optional[int] = None,
name: typing.Optional[str] = None,
pay_info: typing.Optional["PayInfoDict"] = None,
) -> "TEmployee":
"""
Construct from a dictionary (eg. a POST payload).
Args:
id: Unique identifier for the employee.
name: The name of the employee.
pay_info: The pay_info of the Employee.
Returns:
Model instance based on the dictionary.
"""
...
@classmethod
def from_str(cls, value: str) -> "TEmployee":
"""
Construct from a JSON string (eg. a POST payload).
Returns:
Model instance based on the JSON string.
"""
...
def to_dict(self) -> EmployeeDict:
"""
Convert to a dictionary (eg. to send back for a GET request).
Returns:
Dictionary based on the model instance.
"""
...
def to_str(self) -> str:
"""
Convert to a JSON string (eg. to send back for a GET request).
Returns:
JSON string based on the model instance.
"""
...
Employee: typing.Type[TEmployee] = models.Employee # type: ignore
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