SQLAlchemy ORM – Working with Joins Now that we have two tables, we will see how to create queries on both tables at the same time. To construct a simple implicit join between Customer and Invoice, we can use Query.filter() to equate their related columns together. Below, we load the Customer and Invoice entities at […]
Category Archives: sqlalchemy
Common Relationship Operators In this chapter, we will discuss about the operators which build on relationships. __eq__() The above operator is a many-to-one “equals” comparison. The line of code for this operator is as shown below − s = session.query(Customer).filter(Invoice.invno.__eq__(12)) The equivalent SQL query for the above line of code is − SELECT customers.id AS […]
SQLAlchemy ORM – Eager Loading Eager load reduces the number of queries. SQLAlchemy offers eager loading functions invoked via query options which give additional instructions to the Query. These options determine how to load various attributes via the Query.options() method. Subquery Load We want that Customer.invoices should load eagerly. The orm.subqueryload() option gives a second […]