Class ForeignKey

Namespace

YndigoBlue.Velocity.Constraints

Assembly

YndigoBlue.Velocity.dll

Represents a foreign key constraint that enforces referential integrity between tables.

public class ForeignKey : Constraint, IEquatable<Constraint>, IComparable<Constraint>

Inheritance

object

Constraint

ForeignKey

Implements

IEquatable<Constraint>

IComparable<Constraint>

Remarks

A foreign key constraint ensures that values in one or more columns match values in the referenced (lookup) table's primary key or unique constraint. Supports cascading actions on UPDATE and DELETE operations.

Examples

using (var manager = new Manager(connection))
{
    var schema = manager.LoadSchema("myschema");

    // Single-column foreign key: orders.customer_id -> customers.id
    Table ordersTable = schema.CreateTable("orders");
    ordersTable.CreateColumn("id", DataType.Integer, autoGenerate: true);
    ordersTable.CreateColumn("customer_id", DataType.Integer);
    ordersTable.CreateColumn("order_date", DataType.Date);

    ForeignKey fk = ordersTable.CreateForeignKey(
        "fk_orders_customers",
        "customer_id",          // source column
        "myschema",             // lookup schema
        "customers",            // lookup table
        "id",                   // lookup column
        ForeignKeyRuleType.Cascade,   // ON DELETE
        ForeignKeyRuleType.Restrict   // ON UPDATE
    );

    manager.CreateTable(ordersTable);
    manager.CreateConstraint(fk);

    // Composite foreign key across multiple columns
    Table orderItemsTable = schema.CreateTable("order_items");
    orderItemsTable.CreateColumn("order_id", DataType.Integer);
    orderItemsTable.CreateColumn("product_id", DataType.Integer);

    ForeignKey compositeFk = orderItemsTable.CreateForeignKey(
        "fk_order_items_products",
        [ "order_id", "product_id" ],
        "myschema",
        "products",
        [ "order_id", "product_id" ],
        ForeignKeyRuleType.Cascade,
        ForeignKeyRuleType.Cascade
    );

    manager.CreateTable(orderItemsTable);
    manager.CreateConstraint(compositeFk);
}

Properties

ConstraintType

Gets the constraint type as ForeignKey.

DeleteRule

Gets the action to take when a row in the referenced table is deleted.

IsComposite

Gets whether this is a composite foreign key (spanning multiple columns).

LookupColumns

Gets the column names in the lookup (referenced) table.

LookupSchema

Gets the schema name of the lookup (referenced) table.

LookupTable

Gets the name of the lookup (referenced) table.

SourceColumns

Gets the column names in the source (referencing) table.

UpdateRule

Gets the action to take when a value in the referenced column is updated.

Methods

IsEqual(Constraint)

Determines whether this constraint is equal to another constraint based on their properties.