Question

I am working with a SQL Library (Programming library, ANSI SQL Compliant, called ABS Database,(http://www.componentace.com/help/absdb_manual/absdbmanual_content.htm). It supports the various joins, CASE, etc…

I have a single table (appt), which is a table of appointments.

ApptKey - Integer - Primary Key
SA_ID -  Integer  (a person’s ID, think employee number),
Layer - Integer – only 4 different values, 1, 2, 3 or 4 (think Appt Category)
Number_Of_Minutes  - Integer – the length of the appointment

Note that some SA_ID/Layer combinations may be empty (i.e. no rows for that combination). Other SA_ID/Layer combinations may have multiple rows (I am not showing other columns as they are not relevant here). I need a report to show the sum of minutes, for each person (SA_ID), for each layer, in one row… i.e. each SA_ID has their own row, showing the sum for Layer =1, the sum for layer =2 , the sum for Layer =3, and the sum for layer = 4.

Example data…

SA_ID         LAYER        Number_of_Minutes
1             1            10
1             1            30
2             1            10
3             2            10
1             4            10

I need a query that gives this result.

SA_ID      LAYER_1     LAYER_2    LAYER_3     LAYER_4
1          40          0          0           10
2          10          0          0           0
3          0           10         0           0

I need this type of format, because this query feeds a Chart/graph component…

I think I need to use a right join a multiple correlated subqueries, but I just can’t get it to work. Is this the right approach. What I have below runs, but as a straight join. Can I (or how do I) rewrite this to use a right outer join? Is a right outer join the best approach?

select g.sa_id,  l1.totalsum, l2.totalsum, l3.totalsum, l4.totalsum
from  (select sa_id, layer, sum(number_of_minutes) totalsum from appt where layer = 1 group by sa_id, layer) l1,
           (select sa_id, layer, sum(number_of_minutes) totalsum from appt where layer = 2 group by sa_id, layer) l2,
           (select sa_id, layer, sum(number_of_minutes) totalsum from appt where layer = 3 group by sa_id, layer) l3,
          (select sa_id, layer, sum(number_of_minutes) totalsum from appt where layer = 4 group by sa_id, layer) l4,
          (select distinct sa_id "sa_id" from appt) g
where
      (l1.sa_id = g.sa_id)
and   (l2.sa_id = g.sa_id)
and   (l3.sa_id = g.sa_id)
and   (l4.sa_id = g.sa_id)

Answer 1

SELECT SA_ID,
SUM(CASE WHEN LAYER = 1 THEN Number_of_Minutes ELSE 0 END) AS LAYER_1, 
SUM(CASE WHEN LAYER = 2 THEN Number_of_Minutes ELSE 0 END) AS LAYER_2,
SUM(CASE WHEN LAYER = 3 THEN Number_of_Minutes ELSE 0 END) AS LAYER_3,
SUM(CASE WHEN LAYER = 4 THEN Number_of_Minutes ELSE 0 END) AS LAYER_4
FROM Appt
GROUP BY SA_ID

EDIT: Because it supports CASE expressions.