Sequence within SQL Select

Question

I\'m having a bit of a problem with using my sequence within a SELECT statement.

SELECT
     c.cust_name,
     c.site,
     customer_id_seq.nextval         


        

Answer 1

for IBM Imformix

In a SELECT statement, you cannot specify NEXTVAL or CURRVAL in the following contexts:

• In the projection list when the DISTINCT keyword is used
• In the WHERE, GROUP BY, or ORDER BY clauses
• In a subquery
• When the UNION operator combines SELECT statements

Answer 2

You cannot use sequences in queries with ORDER BY.

Remove the ORDER BY or put in into a subquery:

SELECT  q.*, customer_id_seq.nextval    
FROM    (
        SELECT  c.cust_name,
                c.site
        FROM    customer c
        WHERE   c.customer_id IS NULL
        ORDER BY
                c.site_code ASC
        ) q

Answer 3

Why don't you use rownum instead of fetching values from sequence?