I discovered today that in Oracle 10g (and I presume in earlier versions also) it is not possible to directly assign a sequence value in to a PLSQL variable, hence neither of the 2 following examples will compile in 10g:

1:

PROCEDURE set_up_test_data(no_of_days NUMBER)
IS
  -- Doesn't compile
  nice_unique_number NUMBER := mysequence.nextval;
BEGIN
  -- do stuff here...
END set_up_test_data;

2:

PROCEDURE set_up_test_data(no_of_days NUMBER)
IS
  nice_unique_number NUMBER;
BEGIN
  -- Doesn't compile.
  nice_unique_number := mysequence.nextval;
  -- do stuff here...
END set_up_test_data;

A bit of googling suggests that a common workaround to this is to be do a SELECT INTO using the dual table, as below:

PROCEDURE set_up_test_data(no_of_days NUMBER)
IS
  nice_unique_number NUMBER;
BEGIN
  --Works nicely
  SELECT mysequence.nextval INTO nice_unique_number FROM dual;
  -- do stuff here...
END set_up_test_data;

Note: This no appears to be an issue as of Oracle 11g (search for Straight Sequences).

EdD