Sqlalchemy primary key multiple columns. Jan 28, 2026 · Python Database Patterns SQLAlchemy 2. Specify the 'foreign_keys' argument, providing a list of those columns which should be counted as containing a foreign key reference to the parent table. , "The Great Gatsby" 1st edition vs. orm import DeclarativeBase, Mapped, mapped_column, Session class Base (DeclarativeBase): pass class User (Base): __tablename__ = "users" id: Mapped[int] = mapped_column(primary_key= True) Jun 10, 2012 · I have a database table which has a compound primary key (id_a, id_b). The setup for each of the following sections is as follows: Jan 18, 2025 · Basic Primary Key Configuration The most straightforward way to define a primary key in SQLAlchemy is using the primary_key=True parameter in column definitions. Dec 15, 2015 · One way from there: In SQLAlchemy ORM, to map to a specific table, there must be at least one column designated as the primary key column; multi-column composite primary keys are of course also perfectly possible. In SQLAlchemy, composite keys are defined by specifying multiple columns as primary keys or using unique=True on a combination of columns. Using a dataclass, these attributes are In this post we will give easy to understand definitions and examples of using foreign keys in our sqlalchemy classes in order to define links / relationships between our tables. May 1, 2020 · Specify the 'foreign_keys' argument, providing a list of those columns which should be counted as containing a foreign key reference from the secondary table to each of the parent and child tables. That's not what they're actually called but I am simplifying for this question. Here's two explains of the same query, first with a single element on the right of the IN, and then with two elements. AmbiguousForeignKeysError: Could not determine join condition between parent/child tables on relationship Address. Sep 9, 2014 · When I run the above code, I get sqlalchemy. Dec 13, 2020 · Using SQLAlchemy I'm a bit confused about composite keys (?), uniqueconstraint, primarykeyconstraint, etc. how do I configure this correctly? May 7, 2010 · 2) Once you have more than one field with primary_key=True you get a model with composite primary key. For a single-column primary key, the scalar calling form is typically the most expedient. Flask-SQLAlchemy simplifies how binds work by associating each engine with a short string, a “bind key”, and then associating each model and table with a bind key. user_id, group_users. 2nd edition). Jun 29, 2014 · 17 I am mapping classes to existed MySQL tables generated by Drupal. So, in this case id will be used in the WHERE clause and then that would be updates using the x value in the dictionary right ? Jun 13, 2017 · It sounds like you have the wrong primary key. A core piece of SQLAlchemy is that we select rows from many things besides physical tables. Under SQLAlchemy 1. In this article, we will explore how to work with multiple tables in SQLAlchemy Core and show some examples. To specify multiple columns in the constraint/index or to specify an explicit name, use the UniqueConstraint or Index constructs explicitly. The library provides transparent primary key handling that works with any column naming convention. sqlalchemy. For any relationship in SQLAlchemy you need to actually define not just the relationship itself but also the foreign key that stores the link in the database. I. group_id], indicating that these two columns should be used in order to construct the identity key for instances of the GroupUsers class. Thank you! Dec 30, 2014 · How to specify table relationships in SQLAlchemy with multi-level/multiple joins? Asked 12 years ago Modified 11 years, 2 months ago Viewed 6k times I'm trying to create a relationship that spans across 3 tables but I can't quite figure out the syntax. Could this perhaps be extended to include sample Table definitions, so it'd make a nice dupe target for Core questions as well. Model to create a model class. billing_address - there are multiple foreign key paths linking the tables. Jul 29, 2020 · The problem is that MySQL doesn't seem to use indexes for multi-column IN statements if there's more than one tuple on the right side. In SQLAlchemy the key classes include ForeignKeyConstraint and Index. metadata, Column('id', Integer, primary_key=True), ) actions = Table('actions', Base. For a composite (e. In SQLAlchemy, you can create a composite primary key by specifying multiple columns in the `primary_key` argument to the `Column` object. composite, primary keys are of course entirely feasible as well. Oct 2, 2013 · I'm trying to use SQLAlchemy with MySQL to create a table mapping for a table with a composite primary key, and I'm unsure if I'm doing it right. The number of child tables can be arbitrary at run time. Jan 1, 2025 · Hello, I am writing a something like a set of linked lists, each node has attributes chat_id and msg_id, and it may have an attribute named reply_id. My problem is with the relationship function, which makes me repeat the information (in the primaryjoin) which I have already given in the ForeightKeyConstraint (violating DRY). Apr 8, 2012 · Extract from the documentation of the Column: unique – When True, indicates that this column contains a unique constraint, or if index is True as well, indicates that the Index should be created with the unique flag. Jul 20, 2024 · Using multiple foreign keys in SQLAlchemy mapped classes with the same primary key is a powerful feature that allows for complex relationships between tables. Though then people can't really change names without incurring a huge multi-table database update as all the foreign keys everywhere have to change. There are a variety of situations where this behavior needs to be customized. Apr 9, 2009 · What is the syntax for specifying a primary key on more than 1 column in SQLite ? Mar 2, 2026 · Basic Relationship Patterns ¶ A quick walkthrough of the basic relational patterns, which in this section are illustrated using Declarative style mappings based on the use of the Mapped annotation type. py - Illustrates a so-called “generic foreign key”, in a similar fashion to that of popular frameworks such as Django, ROR, etc. The existing table is defined with the composite primary key. 'primary_key' in __mapper_args__ just instructs mapper to use these fields as identity. Aug 16, 2020 · 0 How to I create a foreign key column that has multiple foreign keys in it? I have a notes table that I would like to keep notes in for many different subjects/tables. How do I create an class that is unique over 2 columns, and refer to that unique combination? Aug 20, 2018 · with python sqlalchemy, how do define multiple-column primary key Ask Question Asked 7 years, 6 months ago Modified 5 years, 6 months ago The primary key of the table consists of the user_id column. Unlike plain SQLAlchemy, Flask-SQLAlchemy’s model will automatically generate a table name if __tablename__ is not set and a primary key column is defined. Mar 15, 2023 · Unlike a composite primary key where you can add primary_key=True to columns you want, composite foreign keys do not work that way. exc. I'm having issues mapping these tables because the child's column parent_id is a Foreign Key to both of the parent tables. I have one parent table which holds the primary keys of several child tables. What is a foreign key in SQLAlchemy? How to provide primary key for multiple column in a single table using PostgreSQL? Example:. future parameter set to False, legacy-style LegacyRow objects are returned which feature the partial-named-tuple behavior of prior SQLAlchemy versions, where containment checks continue to use key containment; "name" in row would return True if the row had a column named “name”, rather than a value. When working with a relational database, it's common to have multiple tables that are related to each other. Aug 8, 2011 · Upon adding a second foreign key to the same table I get the following error: Please specify the 'onclause' of this join explicitly. The others are just relationships between posts and entities that are not to be pk'd. Defining Foreign Keys ¶ A foreign key in SQL is a table-level construct that constrains one or more columns in that table to only allow values that are present in a different set of columns, typically but not always located on a When a non-prime attribute column in one table references the primary key and has the same column as the column of the table which is prime attribute is called a foreign key. Whether it’s a one-to-many or many-to-many relationship, SQLAlchemy provides the necessary tools to define and manage these relationships. Column class, we should use the class sqlalchemy. There are no foreign keys between the tables. Flask-SQLAlchemy supports various relationship types, each serving different purposes and modeling scenarios. Mar 22, 2016 · #location id id2 = Column(Integer, ForeignKey('table2. The above mapping, when we attempt to use it, will produce the error: sqlalchemy. So one parent (mother or father) has multiple children. Jul 15, 2019 · 16 Let's consider 3 tables: books American authors British authors Each book has a foreign key to its author, which can either be in the American table, or the British one. A good style would be to setup some relations and a primary key for permissions (actually, usually it is good style to setup primary keys for everything, but whatever): Nothing is wrong with the above code. ArgumentError: Could not locate any simple equality expressions involving locally mapped foreign key columns for primary join condition 'child. This approach is commonly used for single-column primary keys. You need to use ForeignKeyConstraint in the __table_args__ tuple like the following. Defining Foreign Keys ¶ A foreign key in SQL is a table-level construct that constrains one or more columns in that table to only allow values that are present in a different set of columns, typically but not always located on a According to the documentation and the comments in the sqlalchemy. I need to relate to tables (one-to-one), but I've got a problem. You should make the name the primary key if that's what you want. Also, what happens if you try to change a name to an existing one? Jun 19, 2015 · In summary: how can I have relationships joined to a table with multiple foreign keys referring to the same key and still preserve cascading (deletion)? Feb 25, 2014 · I am trying to figure out the correct join query setup within SQLAlchemy, but I can't seem to get my head around it. id'), primary_key=True) Combination of id1 and id2 has to always be unique, and combination of those 2 are used to identify the items. Would anyone be able to identify what I am Mar 2, 2026 · Basic Relationship Patterns ¶ A quick walkthrough of the basic relational patterns, which in this section are illustrated using Declarative style mappings based on the use of the Mapped annotation type. Sep 5, 2024 · The SQLAlchemy ORM, in order to map to a particular table, needs there to be at least one column denoted as a primary key column; multiple-column, i. My version is below. Aug 6, 2015 · is there any performance-difference between using multiple filter() methods and using the combination of multiple conditions (by or_ or and_) in a single filter, on large mysql tables? Sep 17, 2021 · If you need to create a composite primary key with multiple columns you can add primary_key=True to each of them: 1 2 3 4 5 6 7 8 9 10 11 Mar 23, 2016 · I'm using SQLAlchemy to programmatically query a table with a composite foreign key. AmbiguousForeignKeysError: Could not determine join condition between parent/child tables on relationship Customer. Defining Foreign Keys ¶ A foreign key in SQL is a table-level construct that constrains one or more columns in that table to only allow values that are present in a different set of columns, typically but not always located on a A primary key is a column or group of columns that uniquely identifies a row in a table. A simple example represents pairs of Integer columns as a Point object, with attributes . Multiple columns may be assigned the primary_key=True flag which denotes a multi-column primary key, known as a composite primary key. Using SQLalchemy core, how can I join multiple child tables to Jul 1, 2023 · The Primary Key and Foreign Key relationship forms the foundation for defining relationships in Flask-SQLAlchemy. Defining Constraints and Indexes ¶ This section will discuss SQL constraints and indexes. SQLAlchemy turns autoincrement on by default on integer primary key columns. SQLAlchemy can also map to views or selects - if a view or select is against multiple tables, now you have a composite primary key by nature. In fact, you don't even need autoincrement=True or db. The table rows can only be paired up by values matching in multiple columns. For example, a book might need both `title` and `edition` to be unique (e. These constraints are defined when creating the table schema using SQLAlchemy's declarative syntax. I know that when I use primary foreign keys from another table I need to define a ForeignKeyConstraint, but when one foreign key is primary and another unique it doesn't work. This isn't to do with multiple relationships specifically. Here is the generic syntax: Mar 29, 2016 · The docs suggest All those keys which are present and are not part of the primary key are applied to the SET clause of the UPDATE statement; the primary key values, which are required, are applied to the WHERE clause. Composite primary keys are not generated automatically since there is ambiguity here: how should subsequent key differ from previous? Mar 2, 2026 · Configuring how Relationship Joins ¶ relationship() will normally create a join between two tables by examining the foreign key relationship between the two tables to determine which columns should be compared. Jan 11, 2024 · Multiple foreign keys in secondary table #10866 Closed Answered by zzzeek klaydev asked this question in Usage Questions Jul 4, 2018 · select * from table1 join table2 using (col1, col2) I am cannot figure out how to make this execute using SQLAlchemy and any help would be appreciated. 0 and database best practices. Here, I've put together a working setup based on yours. When using an unsortable enumeration object such as a Python 3 Enum object, this parameter may be used to set a default sort key function for the objects. AmbiguousForeignKeysError: Could not determine join condition between parent/child tables on relationship Person. someone can keep a note against a user or a service. Queries are executed through db. 4, when create_engine. How can I implement such foreign key condition in SQLAlchemy? I'd like to have a single column to handle the link. : CREATE TABLE example ( id INT NOT NULL, date TIMESTAMP NOT NULL, data VARCHAR(128) PRIMARY KEY (id, date) May 10, 2012 · I have a set of tables that look like: workflows = Table('workflows', Base. Both fields are primary keys. The foreign key is the “joint” that connects together pairs of rows which have a relationship with each other, and SQLAlchemy assigns very deep importance to this concept in virtually every area of its operation. Jun 23, 2012 · Is the id column necessary? Most of the tutorials I've seen have that as a column (primary key specifically). Sep 5, 2024 · The Mapper does not automatically inspect unique constraints for primary keys; instead, we make use of the mapper. ArgumentError: Mapper Mapper|MyMainTable|main_table could not assemble any primary key columns for mapped table 'main_table' Is there any way to add the PK declaration this way? Mar 2, 2026 · Defining Constraints and Indexes ¶ This section will discuss SQL constraints and indexes. And relation map is not applied to a primary key. Sep 5, 2024 · Mapping Columns and Expressions ¶ The following sections discuss how table columns and SQL expressions are mapped to individual object attributes. Apr 6, 2021 · Specify the 'foreign_keys' argument, providing a list of those columns which should be counted as containing a foreign key reference to the parent table. This is a departure from single-field keys, which are typically denoted with a primary_key=True flag within the column definition. Perhaps the question could be edited to accommodate the change as well. c. Apr 7, 2025 · In SQLAlchemy, these objects descend from Selectable, the most prominent I’m looking to join multiple tables and selecting specific columns using Flask-SqlAlchemy. y. In SQLAlchemy, you define composite primary keys directly within the table definition by using the PrimaryKeyConstraint construct. How can I specify this relationship? class Parent(Base): Sep 5, 2024 · Configuring how Relationship Joins ¶ relationship() will normally create a join between two tables by examining the foreign key relationship between the two tables to determine which columns should be compared. Any help would be appreciated. It lays the relation between the two tables which majorly helps in the normalization of the tables. multiple column) primary key, a tuple or dictionary should be passed. What you have right now is two different foreign keys and not a single composite foreign key. 0 Documentation Home Download this Documentation Previous: Next: Up: On this page: Composite Column Types Working with Mapped Composite Column Types Other mapping forms for composites Map columns directly, then pass to composite Map columns directly, pass attribute names to composite Imperative mapping and imperative table Using Legacy Non-Dataclasses Tracking In-Place Mutations Apr 21, 2018 · How to specify primary key on multiple columns in SQLite? In SQLite, you can specify the primary key of a table on multiple table columns. 0 Basics from sqlalchemy import create_engine, select from sqlalchemy. Handling Multiple Join Paths ¶ One of the most common situations to deal with is when there are more than Apr 10, 2024 · sqlalchemy. primary_key parameter, passing a collection of [group_users. How can I "refresh" my database. g. The ORM provides a single attribute which represents the group of columns using the class you provide. It refers to different engines as “binds”. Mar 2, 2026 · SQLAlchemy 2. Notice only id is a primary key. Jun 27, 2023 · Key Benefits of Using Composite Columns in SQLAlchemy Improved Data Organization: Composite columns allow you to logically group related data into a single attribute, enhancing code readability Feb 27, 2018 · SQLAlchemy multiple foreign keys in one mapped class to the same primary key Ask Question Asked 12 years ago Modified 8 years ago Defining Models ¶ See SQLAlchemy’s declarative documentation for full information about defining model classes declaratively. I have tried using the foreign_keys argument from inside the User class, but that did nothing. See SQLAlchemy’s Querying Guide and other SQLAlchemy documentation for more information about querying data with the ORM. SQLAlchemy-Searchable provides a number of customization options for the automatically generated search trigger, index and search vector columns. Multiple Databases with Binds SQLAlchemy can connect to more than one database at a time. The three main relationship types are one-to-one, one-to-many, and many-to-many. I can not define foreign key without a primary key. I have 3 tables TableA, TableB and TableC and the relationship I'm trying to model is: TableA. property - there are multiple foreign key paths linking the tables. Handling Multiple Join Paths ¶ One of the most common situations to deal with is when there are more than Feb 28, 2026 · SQLAlchemy Core is a lightweight and flexible SQL toolkit that provides a way to interact with relational databases using Python. Subclass db. However, the exa 联合主键（又称复合主键、多重主键）是一个表由多个字段共同构成主键 (Primary Key)。 在 Sqlalchemy 中有两种方式可定义联合主键： 方法一：多个字段中定义 primary_key=True;方法二：使用 table_args 特殊属性。… Nov 29, 2017 · Please manually specify a unique column to use as id_field " but I don't have a single unique column in my table as it is an exposed association table for a many-to-many relationship of two other tables . toy_shares. execute(). The current code is import sqlalchemy import sq Aug 28, 2023 · Understanding Composite Primary Keys: A composite primary key consists of two or more columns that together form a unique identifier for a row in a table. session. id' on relationship Parent. we ll cover I’m getting errors with my attempts as I believe my join statements are wrong Any Self Differentiation: — Behaviours Linked Seit 174 Jahren: Gefell Strahlt Weit Ins Mar 2, 2026 · Composite Column Types ¶ Sets of columns can be associated with a single user-defined datatype, which in modern use is normally a Python dataclass. SQLAlchemy 2. Index to specify an index that contains multiple columns. A composite key consists of two or more columns that together uniquely identify each record in a table. Sep 5, 2024 · The association table contains a “discriminator” column which determines what type of parent object associates to each particular row in the association table. Two tables have the column nid. Let's start with an example database in which we have a User class and an associated Address class. The setup for each of the following sections is as follows: Mar 30, 2021 · Configuring how Relationship Joins ¶ relationship() will normally create a join between two tables by examining the foreign key relationship between the two tables to determine which columns should be compared. id_a is a foreign key and id_b is just an integer, "sequence number" so to speak. When working with object-relational mappers (ORMs) like SQLAlchemy, setting up relationships involving composite May 28, 2025 · Primary Key Handling Relevant source files This document covers how sqlalchemy-crud-plus automatically detects and handles primary keys in SQLAlchemy models, including both single and composite primary key scenarios. Mar 2, 2026 · The SQLAlchemy ORM, in order to map to a particular table, needs there to be at least one column denoted as a primary key column; multiple-column, i. I have the following table setup (simplified, I left out the non-essential fiel Mar 2, 2026 · The SQLAlchemy ORM, in order to map to a particular table, needs there to be at least one column denoted as a primary key column; multiple-column, i. @ymfoi ORM configuration doesn't affect table schema. Mar 25, 2024 · When you have a composite primary key consisting of multiple columns, instead of declaring each column as a primary key separately, it is more efficient and organized to define a primary key Sep 5, 2024 · The SQLAlchemy ORM, in order to map to a particular table, needs there to be at least one column denoted as a primary key column; multiple-column, i. As these belong to a Table and not Feb 24, 2026 · The SQLAlchemy ORM, in order to map to a particular table, needs there to be at least one column denoted as a primary key column; multiple-column, i. Note also that each column describes its datatype using objects corresponding to genericized types, such as Integer and String. SQLAlechemy's ORM will take care of generating id's and populating objects with them if Jul 22, 2024 · SQLAlchemy supports the full spectrum of database constraints such as NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK, and DEFAULT. Sequence('seq_reg_id', start=1, increment=1), as SQLAlchemy will automatically set the first Integer PK column that's not marked as a FK as autoincrement=True. . For example, the following code creates a table of students with a composite primary key consisting of the student’s name and student ID number: python from Dec 12, 2025 · In database design, **composite keys** (primary keys composed of multiple columns) are essential when a single column cannot uniquely identify a record. Aug 18, 2017 · I have tried a few ways to import the two keys from reports and use as primary keys. May 16, 2015 · "posts_subject_2_fkey" FOREIGN KEY (subject_2) REFERENCES entities(id) I'm trying to figure out how to define the orm object for "posts" to include all 3 of the foreign keys. Jan 13, 2017 · 6 In SQLAlchemy, imagine we have a table Foo with a compound primary key, and Bar, which has two foreign key constrains linking it to Foo (each Bar has two Foo objects). Handling Multiple Join Paths ¶ One of the most common situations to deal with is when there are more than Oct 7, 2022 · The SQLAlchemy docs include a guide on migrating tables, (as well as a great overview on relationships in general), however, this guide assumes you are using foreign key constraints in your models and using the auto-incrementing primary key field as your reference. Can I do without it? Especially in cases where I have another primary key? How can I have a composite key constraint on Candidate#Name and Candidate#post_id columns, given that post_id is a foreign key. What do I need to define on my models to fix this issue? The SQLAlchemy ORM requires that primary key columns which are mapped must be sortable in some way. generic_fk. user - there are multiple foreign key paths linking the tables. If you wish to disable autoincrement behavior, you must set x-autoincrement to false. e. x and . parent_id = parent. e. The referenced columns almost always define the primary key for their owning table, though there are exceptions to this. Mar 30, 2021 · The SQLAlchemy ORM, in order to map to a particular table, needs there to be at least one column denoted as a primary key column; multiple-column, i. schema. Jun 8, 2017 · sqlalchemy. id1 isn't enough since databases can be in several locations and tables are synchronized time to time. jrlofrhqhtghbubvczkzpydobmtivtniupevuthqtvbzqqeocs