Case statement in where

Question

I am writing a query to get all the invoices with amount > 100 for US > 200 for CAN and > 1200 for mxn ( mexico)

Invoice_Header table ( total amount and company id) Company table (company id and currency id) currency table ( currency id and currency)

  SELECT IH.Invoice_Num , IH.invoice_amount , IH.invoice_date
  FROM Invoice_Header IH ,
       company c,
       Currency cu
  WHERE  IH.Company_oid = c.Company_oid
  AND    c.currency_oid = cu.currency_oid
  AND 
     CASE IH.total = 
         WHEN cu.code = 'USA' then IH.total > 100
         WHEN cu.code = 'CAN' then IH.total > 200
         WHEN cu.code = 'MXN'  then IH.total > 1200
     END

I am getting syntax errors when trying to run this on a oracle database.

Answer 1

I wouldn't use a CASE statement here. It sounds like you want some basic boolean logic

AND(   (cu.code = 'USA' and ih.total > 100)
    OR (cu.code = 'CAN' and ih.total > 200)
    OR (cu.code = 'MXN' and ih.total > 1200))

If you really wanted to use a CASE statement for some reason, you could do something like

AND 1 = (CASE WHEN cu.code = 'USA' and ih.total > 100 
              THEN 1
              WHEN cu.code = 'CAN' and ih.total > 200
              THEN 1
              WHEN cu.code = 'MXN' and ih.total > 1200 
              THEN 1
              ELSE 0
           END)

Answer 2

I would try something like

  SELECT IH.Invoice_Num , IH.invoice_amount , IH.invoice_date
  FROM Invoice_Header IH ,
       company c,
       Currency cu
  WHERE  IH.Company_oid = c.Company_oid
  AND    c.currency_oid = cu.currency_oid
  AND (   (cu.code = 'USA' and IH.total > 100)
       OR (cu.code = 'CAN') and IH.total > 100)
       OR (cu.code = 'MXN') and IH.total > 1200)) 

if you really need to use a CASE in the where clause you could do something like

SELECT 'WEEK-END' AS col_a
  FROM DUAL
 WHERE 1 = CASE
             WHEN to_char(sysdate, 'Day') = 'Saturday' then 1
             WHEN to_char(sysdate, 'Day') = 'Sunday' then 1 
             else 0
           END