User_id INTEGER NOT NULL REFERENCES user(user_id),Ĭreate_all() creates foreign key constraintsīetween tables usually inline with the table definition itself, and for this table is employees # get the table related by a foreign key list ( employees. key # access a column's table: employees. foreign_keys # get the "key" of a column, which defaults to its name, but can # be any user-defined string: employees. bind # access a column's name, type, nullable, primary key, foreign key employees. metadata # access the table's bound Engine or Connection, if its MetaData is bound: employees. foreign_keys : print fkey # access the table's MetaData: employees. primary_key : print primary_key # get the table's foreign key objects: for fkey in employees. c : print c # get the table's primary key columns for primary_key in employees. c # iterate through all columns for c in employees. # access the column "EMPLOYEE_ID": employees. In creating real schema generation scripts.Ī collection of metadata entities is stored in an object aptly named They are therefore most intuitive to those who have some background SQLAlchemy to load all the additional information related to that name from aĪ key feature of SQLAlchemy’s database metadata constructs is that they areĭesigned to be used in a declarative style which closely resembles that of Process called reflection, which means you start with a single object suchĪs Table, assign it a name, and then instruct It can also be generated by SQLAlchemy using a Sequence, all of which are imported from the Types of operations - issuing CREATE and DROP statements (known as DDL),Ĭonstructing SQL queries, and expressing information about structures thatĭatabase metadata can be expressed by explicitly naming the various componentsĪnd their properties, using constructs such as These objects are at the core of three major The core of SQLAlchemy’s query and object mapping operations are supported byĭatabase metadata, which is comprised of Python objects that describe tablesĪnd other schema-level objects. Creating/Dropping Foreign Key Constraints via ALTER.Binding MetaData to an Engine or Connection.
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