Create another App Table (mileage_entry)

You won’t be surprised to learn the process is basically the same, for adding the second and subsequent tables. Go through the New App Table Wizard as before, giving details for the desired table.

See Create the first App Table (vehicle) to revisit all the gory details.

Here are the specs we’ll go with for this entry table. Note that we disable versioning history for this table, since there is “no need” for it. If you feel differently, enable it.

  • Table Name - poser_mileage_entry

  • Model Class - MileageEntry

  • Model Title - Mileage Entry

  • Model Title Plural - Mileage Entries

  • Description - Represents a “mileage entry” recorded at time of fillup.

  • Versioning - disabled

And for Columns:

  • date - date, not nullable

  • vehicle_uuid - FK (see below), not nullable

  • fillup_gallons - numeric(7, 3)

  • fillup_payment - numeric(6, 2)

  • odometer - integer

  • notes - text

Note that we’re allowing nulls for the fillup and odometer values. This is just to keep things practical since in the real world you might just want to enter what data you have, even if you’re doing it days after the fact and no longer have it all. But that’s a judgment call and you can design however you want.

One complicating factor for our entry table, as compared to the vehicle table, is that we want each entry record to reference a vehicle record.

Referencing another Table via foreign key

It’s possible to define a “typical” foreign key column, and even get a SQLAlchemy ORM “relationship” setup properly within the generated code. Really “typical” is the keyword, but thankfully that’s what our little tutorial app calls for here.

(And we’re just commenting on the wizard here - since it’s just SQLAlchemy under the hood, you can do whatever you want outside of the wizard.)

When adding the FK column (in 1st step of wizard), the convention is to name the column with a _uuid suffix. For instance here we name it vehicle_uuid since that’s what we intend to reference.

For data type, choose “UUID+FK” and then choose the appropriate reference table. It would be vehicle except you may recall, we gave it a custom prefix, so in fact poser_vehicle is the table we’ll select here.

(Un)Checking the nullable flag works as expected here; for the tutorial we want it unchecked so each mileage entry requires a vehicle reference.

And finally the relationship, this should be named something sane and simple as it will be used in a Python context. For instance from a given mileage entry record, we can directly access its related vehicle record by way of this relationship. In this example we just use vehicle for the relationship name.

Note that for this kind of FK field, the Description you provide will be set on the relationship instead of the column proper.