- Instance
- Constructor
Instance Methods
An instance method operates on a specific instance of a distinct or structured UDT. For example, an instance method named area might calculate and return the area of a structured UDT named circle that contains attributes x, y, and radius.
You can replace a column name in an SQL expression with an instance method invocation on a UDT. When Vantage evaluates the expression, it invokes the UDM.
Instance methods can also provide transform, ordering, and cast functionality for a distinct or structured UDT. You do not invoke these types of instance methods directly. Vantage uses this functionality during certain operations involving the UDT.
| WHEN you … | THEN Vantage uses this functionality … |
|---|---|
| convert the UDT to a predefined data type or another UDT, for example with the CAST function | cast |
| convert another UDT or predefined data type to the UDT | |
| compare two UDTs, for example with the ORDER BY clause | ordering |
| export the UDT from the server | transform Vantage also uses transform functionality to import the UDT to the server, for example with the USING modifier. However, the implementation is always a UDF, not a UDM. |
Before you can create a table that has a UDT column and perform queries on the column, the UDT must have UDFs or instance methods associated with it that provide transform, ordering, and cast functionality.
| IF the UDT is … | THEN … |
|---|---|
| distinct | Vantage automatically generates UDFs and methods that provide transform, ordering, and cast functionality. |
| structured | you are responsible for implementing UDFs or UDMs that provide cast, ordering, and transform functionality. |
Constructor Methods
A constructor method initializes an instance of a structured UDT.
A structured UDT can have more than one constructor method, each one providing different initialization options.
To create an instance of a structured UDT in an SQL statement, you can invoke the constructor method or specify the constructor method in a NEW expression.