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CHAPTER 6 Using Procedures and Batches
245
Passing parameters to procedures
You can take advantage of default values of stored procedure parameters with
either of two forms of the CALL statement.
If the optional parameters are at the end of the argument list in the CREATE
PROCEDURE statement, they may be omitted from the CALL statement. As
an example, consider a procedure with three INOUT parameters:
CREATE PROCEDURE SampleProc( INOUT var1 INT
DEFAULT 1,
INOUT var2 int DEFAULT 2,
INOUT var3 int DEFAULT 3 )
...
We assume that the calling environment has set up three variables to hold the
values passed to the procedure:
CREATE VARIABLE V1 INT;
CREATE VARIABLE V2 INT;
CREATE VARIABLE V3 INT;
The procedure SampleProc may be called supplying only the first parameter as
follows:
CALL SampleProc( V1 )
in which case the default values are used for var2 and var3.
A more flexible method of calling procedures with optional arguments is to
pass the parameters by name. The
SampleProc procedure may be called as
follows:
CALL SampleProc( var1 = V1, var3 = V3 )
or as follows:
CALL SampleProc( var3 = V3, var1 = V1 )
Passing parameters to functions
User-defined functions are not invoked with the CALL statement, but are used
in the same manner that built-in functions are. For example, the following
statement uses the
fullname function defined in “Creating user-defined
functions” to retrieve the names of all employees:
SELECT fullname(emp_fname, emp_lname) AS Name
FROM employee