The opaque type name
This opaque type name is optional; its presence affects the declaration
as follows:
- When you omit opaque type from the lvarchar declaration,
the database server attempts to identify the appropriate support and
casting functions to use when it converts between lvarchar and
the opaque data type.
You can use the lvarchar host variable to hold data for several different opaque types (as long as the database server is able to find the appropriate support functions).
- When you specify opaque type in the lvarchar declaration,
the database server knows precisely which support and casting functions
to use when it converts between lvarchar and the opaque data type.
Using opaque type can make data conversion more efficient. In this case, however, the lvarchar host variable can hold data only for the specified opaque type.
In the declaration of an lvarchar host variable, the name
of the opaque type must be a quoted string.
Important: Both
the quotation mark (') and the double quotation mark (") are valid
quote characters in lvarchar declarations. However, the beginning
quote and ending quote characters must match.