Runtime values as arguments
The statement-local variable (SLV) and host variable types of arguments supply values as the function executes.
Statement-local variables
The parameter
list of a UDR can include an OUT keyword that the UDR uses to pass
information back to its caller. The following example shows a CREATE
FUNCTION statement with an OUT parameter:
CREATE FUNCTION stem(column LVARCHAR, OUT y CHAR)...In
an SQL statement, the argument that corresponds to the OUT parameter
is called a statement-local variable, or SLV. The SLV argument appears
as a variable name and pound sign (#), as the following example shows:
SELECT...WHERE stem(lname, y # CHAR)For more information about output parameters, the OUT keyword, and SLVs, see the HCL® Informix® User-Defined Routines and Data Types Developer's Guide.
Host variables
While a client application
executes, it can calculate values and pass them to a function as an
input parameter. Another name for the input parameter is host variable.
In the SQL statement, a question mark (?) represents the host variable,
as the following example shows:
SELECT...WHERE equal(lname, ?)The
SET parameter in the following example contains both explicit values
and a host variable:
SELECT...WHERE in(SET{'Smith', 'Smythe', ?}, lname)Because the value of a host variable applies to every row in the table, the access method treats the host variable as a constant. However, the constant that the client application supplies might change during additional scans of the same table. The access method can request that the optimizer re-evaluate the requirements of the qualification between scans.
For more information about the following topics,
see the manual indicated.
| Topic | Manual |
|---|---|
| Setting values for host variables in client applications | HCL® Informix® Enterprise Replication Guide |
| Using functions from client applications | HCL® Informix® DataBlade® API Programmer's Guide |
| Using host variables in SQL statements | HCL® Informix® Guide to SQL: Syntax |