Using fromsql Transform Routines | CREATE TRANSFORM | Teradata Vantage - Rules For fromsql Transform Routines - Analytics Database - Teradata Vantage

A fromsql routine transforms a UDT to a predefined data type.

The fromsql transforms are commonly used both utilities and by some commonly invoked SQL statements.

The following example shows an operation that causes implicit invocation of the fromsql transform routine.

Suppose a client application executes a SELECT statement whose column list contains a UDT column or expression. The following sequence of events occurs.

1. The system implicitly invokes the fromsql transform routine of the defined transform group for that UDT to map the UDT value to a predefined data type value.
2. The client application receives the predefined type value.

For example, consider the following example:

SELECT udt_column
FROM table1;

The fromsql transform routine converts the values of udt_column into the corresponding predefined data type values before returning them to the client application. If the UDT does not have a defined transform or if its transform group does not have a defined fromsql routine, the request aborts and the system returns an error to the requestor.