---

NOTE

The information contained in this document represents information about preview features of the product. Features might change when the product is released for general availability.

---

Implicit Relationships

Implicit relationships link rows in tables by defining a relationship between fields in those tables.

In the Data Definition Language (DDL) file you specify a Value Linked Reference that will establish the relationship. An implicit relationship is defined similarly to an explicit relationship except that you use a where clause to specify the fields that define the relationship.

field_name references table_name [using [table_name].field_name] where table_1.field = table_2.field

The relationship is considered implicit because links between rows are created automatically based on the values of their linked fields as specified by the where clause. This relationship is data-dependent: the linked fields in two related rows must have identical values.

options

using: Indicates the reference in the referenced table for the current reference definition to match. It is only needed when you have more than one reference between the two specified tables.

Forward References

Forward References allow an identifier to reference an entity whose definition appears after the identifier. In other words, the order of the data definition statements does not matter.

In Gaia DDL you build a statement that include a Forward Reference by including all of the statement segments in a single statement terminated by a semicolon. For example, the following DDL segment defines two tables: doctor and patient. The doctor table creates a reference to the patient table, which is defined after the doctor table.

create table doctor (
 name string,
 patients references patient[]
)

create table patient (
 name string,
 doctor references doctor.patients
);

If the doctor table definition is terminated with a semicolon, the compilation of the DDL will fail since the patient table has not yet been defined.