Normally arguments in a procedure call are bound to formal parameters from left to right, as is the default behavior in any programming language. If a default value is specified for a parameter in the procedure definition this parameter is optional and the default value will be assigned to it if the caller does not specify a value. A call may consist of zero or more positional arguments followed by zero or more keyword arguments. A positional argument is any scalar expression. A keyword argument is marked with the syntax:

NAME => scalar_exp

This notation specifies that the expression is to be bound to the parameter NAME in the procedure declaration. The names are matched case-insensitively in all case modes. After all leading positional arguments have been bound to the matching formal parameters in the procedure definition, each keyword argument is bound to the parameter of the same name. After this all unbound formal parameters are assigned to their default values. If a parameter with no default remains unbound an error is signalled. OUT and INOUT parameters are always required, regardless of the mode of calling.

An expression can be passed as INOUT or OUT, but in that case the output value assigned by the procedure is not accessible in the caller. The output value is only accessible if the actual parameter is a variable or parameter.

Arguments of procedures are always evaluated left to right.

create procedure kwd (in k1 int := 111, inout k2 int, in k3 int := 333)
{
  result_names (k1, k2, k3);
  result (k1, k2, k3);
}

kwd (1,1+1,3);
-- results 1,2,3

kwd ();
-- error because inout parameters are always required

kwd (k2=>1);
-- error because a constant is not a suitable value for an inout parameter.

kwd (k2=>1+2);
-- result 111, 2, 333

kwd (k3=>3, k1=>1,k2=>1+1);
-- result 1, 2, 3

kwd (1, k2=>1+1);
-- result 1, 2, 333
kwd (1);
-- error, k2 is required
kwd (badkey=>2, k2=>2+1);
-- error, badkey not a parameter of the function

create procedure kwd2 (in k1 int , in k2 int, in k3 int)
{
  result_names (k1, k2, k3);
  result (k1, k2, k3);
}

kwd2 (k1=>1, k2=>2, k3=>3);
-- result 1, 2, 3
kwd2 (1,2,3);
-- result 1, 2, 3