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docs: document ReferentialAction on ForeignKey #401

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20 changes: 20 additions & 0 deletions typed_sql/doc/05_foreign_keys.md
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Expand Up @@ -98,6 +98,26 @@ abstract final class Book extends Row {
> support for composite foreign keys in the future. But in most cases, you
> should probably avoid such constructs when possible.

## Referential actions

When defining a foreign key, you can specify how the database should react when the referenced row is updated or deleted. This is done using the `onDelete` and `onUpdate` parameters of the `@References` and `@ForeignKey` annotations, passing a `ReferentialAction` enum value:

* `ReferentialAction.noAction`: Prevent the action, or defer the check until the end of the transaction (default).
* `ReferentialAction.restrict`: Prevent the deletion or update of a referenced row immediately.
* `ReferentialAction.cascade`: Delete or update the child table when the referenced row is deleted or updated.
* `ReferentialAction.setNull`: Set the foreign key columns in the child table to `NULL`.
* `ReferentialAction.setDefault`: Set the foreign key columns in the child table to their default values (not supported by InnoDB in MySQL/MariaDB).

```dart schema_references_test.dart#book-model-actions
@References(
table: 'authors',
field: 'authorId',
onDelete: ReferentialAction.cascade,
onUpdate: ReferentialAction.restrict,
)
int get authorId;
```


## Following references in a query (using reference `name`)
With the `@References` annotation in place, `package:typed_sql` will use
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