Question

I am returning a query with names, courses and course codes, but where the course code is null i would like to display “NOT ENROLLED”.
Could I do this by using a ‘default’?
The select statement is coming from a VIEW would this make any difference.

CREATE VIEW STUDENT_LIST
(studentname, dateofbirth, coursecode)
AS 
SELECT COURSECODE, STUDENTNAME, DATEOFBIRTH
FROM STUDENT;

SELECT STUDENTNAME, DATEOFBIRTH, NVL(COURSECODE,"NOT_ENROLLED")
FROM STUDENT_LIST;

I get the reply NOT ENROLLED invalid identifier… I have tried without quotes
I am using oracle.

Answer 1

ORACLE has NVL()

SQL Server has ISNULL()

MySQL has IFNULL()

All of the above and PostgreSQL support COALESCE().

So,

SELECT STUDENTNAME, 
       DATEOFBIRTH, 
       NVL(COURSECODE,'NOT_ENROLLED') 
FROM STUDENT_LIST;

or

SELECT STUDENTNAME, 
       DATEOFBIRTH, 
       COALESCE(COURSECODE,'NOT_ENROLLED') 
FROM STUDENT_LIST;

in Oracle.