![]() I suspect that this easy-to-make mistake is the reason this question has such a huge number of views - over 16000 at the time that I post this answer. The sqlalchemy orm needs a primary key for each. ODI creates a connection (if one did not already exist), and also creates the. Therefore, key types should be specified in the initial migration when the database is created. ![]() Changing the PK typically involves dropping and re-creating the table. to op.create_table() or the Table() constructor) and others that involve declaring a class with Columns as class properties, it's really easy to run into this error by cutting and pasting Column declarations from the first syntax to the second and forgetting to remove some of the commas. As the exception message says, sqlalchemy could not assemble any primary key columns for mapped table users. The mapping editor consists of the sections described in Table 8-1. A change to the PK column's data type after the database has been created is problematic on many database systems. If you simply replace application_essay_id = db.Column(Īside: since SQLAlchemy (and Alembic and Flask-SQLAlchemy) contain some syntaxes for declaring models/tables that involve passing a comma-separated sequence of Columns as arguments (e.g. This stops SQLAlchemy from "seeing" that the columns are present, and consequently causes your model not to contain any primary key column. You get this error because you have trailing commas after your Column() definitions, which cause application_essay_id and theme_essay_id to each be parsed as a one-element tuple containing a Column instead of just a Column.
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