Question

I am trying to add a CASE statement to the end of my SQL query to compute a value depending upon another table value and a previously computed value in the SELECT. The error is returned that DelivCount is an invalid column name. Is there a better way to do this or am I missign something?

SELECT jd.FullJobNumber, jd.ProjectTitle, jd.ClientName, jd.JobManager, jd.ProjectDirector, jd.ServiceGroup, jd.Status, jd.HasDeliverables, jd.SchedOutsideJFlo, jd.ReqCompleteDate,(SELECT COUNT(*)FROM DeliverablesSchedule ds WHERE jd.FullJobNumber = ds.FullJobNumber) as DelivCount, SchedType = 
    CASE 
        WHEN (jd.SchedOutsideJFlo = 'Yes')
            THEN 'outside'
        WHEN (jd.HasDeliverables = 'No ')
            THEN 'none'
        WHEN (DelivCount > 0)
            THEN 'has'
        WHEN (jd.HasDeliverables = 'Yes' AND DelivCount = 0)
            THEN 'missing'
        ELSE 'unknown'
    END
FROM JobDetail jd

Answer 1

try this, which should run a lot faster:

SELECT 
    jd.FullJobNumber, jd.ProjectTitle, jd.ClientName, jd.JobManager, jd.ProjectDirector, jd.ServiceGroup, jd.Status, jd.HasDeliverables, jd.SchedOutsideJFlo, jd.ReqCompleteDate
        ,ds.DelivCount
        ,SchedType =CASE 
                        WHEN (jd.SchedOutsideJFlo = 'Yes')
                            THEN 'outside'
                        WHEN (jd.HasDeliverables = 'No ')
                            THEN 'none'
                        WHEN (ds.DelivCount > 0)
                            THEN 'has'
                        WHEN (jd.HasDeliverables = 'Yes' AND ds.DelivCount = 0)
                            THEN 'missing'
                        ELSE 'unknown'
                    END
    FROM JobDetail jd
        LEFT OUTER JOIN (SELECT
                             FullJobNumber, COUNT(*) AS DelivCount
                             FROM DeliverablesSchedule
                             GROUP BY FullJobNumber
                        ) ds ON jd.FullJobNumber = ds.FullJobNumber

The original query uses a subquery:

A subquery is a SELECT query that
returns a single value and is nested
inside a SELECT, INSERT, UPDATE, or
DELETE statement, or inside another
subquery. A subquery can be used
anywhere an expression is allowed.

by the very nature of a sub query, it must be run repeatedly, once for each row. I have rewritten the query to use a derived table, which is evaluated one time to find all of the counts and is then joined to the proper rows. This allows for the DelivCount value to be referred to as any column would be when joined from another table, and should speed up this query.