Question

I have the following query and I’m trying to update table1 with the Total amount.
Is there anyway to do this in 1 step?

select e.id
     , p.id
     , case  
         when count(distinct e.item) = 1 then 100
         when count(distinct e.item) = 2 then 150
         when count(distinct e.item) = 3 then 200
         when count(distinct e.item) = 4 then 225
         when count(distinct e.item) = 5 then 275
         when count(distinct e.item) = 6 then 325
         when count(distinct e.item) = 7 then 375
         when count(distinct e.item) = 8 then 450
         when count(distinct e.item) = 8 then 470
       end as TotalPay
  from table1 p 
  join table2 e on e.id = '111111'
               and p.id=e.itemid
group by e.id, p.id

Answer 1

Use:

UPDATE TABLE1
   SET total = (SELECT CASE
                         WHEN COUNT(DISTINCT t2.item) = 1 THEN 100
                         WHEN COUNT(DISTINCT t2.item) = 2 THEN 150
                         WHEN COUNT(DISTINCT t2.item) = 3 THEN 200
                         WHEN COUNT(DISTINCT t2.item) = 4 THEN 225
                         WHEN COUNT(DISTINCT t2.item) = 5 THEN 275
                         WHEN COUNT(DISTINCT t2.item) = 6 THEN 325
                         WHEN COUNT(DISTINCT t2.item) = 7 THEN 375
                         WHEN COUNT(DISTINCT t2.item) = 8 THEN 450
                         WHEN COUNT(DISTINCT t2.item) = 9 THEN 470
                       END
                  FROM TABLE2 t2
                 WHERE t2.itemid = id
                   AND t2.id = '111111'
              GROUP BY t2.id, t2.itemid)
 WHERE EXISTS(SELECT NULL
                FROM TABLE2 t
               WHERE t.itemid = id
                 AND t.id = '111111')

• The WHERE clause is necessary, otherwise all the TABLE1 rows will be processed. Those who don’t have related TABLE2 rows, would’ve been updated to NULL
• Oracle (IME, up to 10g) doesn’t support JOINs in an UPDATE clause like MySQL & SQL Server — you have to use a subquery (correlated in this example). It also doesn’t allow you to define a table alias for the table being updated, so when a table alias is omitted like you see in the example — the column is coming from the table without an alias (the one being updated)