Conversion error when using case statement - Sql Server - sql

Question

I have the following query:
select *,
case when prod='CPU' and quan>1000 then 1000
when prod='MOUSE' and quan>1024 then 1024
when prod='MONITOR' and quan<2 then 2 else quan end as quan
from products_test;
I'm getting the error: Conversion failed when converting the varchar value 'CPU' to data type int.

Answer 1

UPDATE: In light of the following comment from author of question
I changed the code code as described by you, but it's still throwing
an error. "Conversion failed when converting the varchar value
'23787.1' to data type int"
It looks like quan in varchar type rather than numeric and also it with the change in error it has been confirmed that prod is defined as integer.
select *,
case when CAST(prod AS VARCHAR(MAX))='CPU' and CAST(quan as DECIMAL(10,4))>1000 then 1000
when CAST(prod AS VARCHAR(MAX))='MOUSE' and CAST(quan as DECIMAL(10,4))>1024 then 1024
when CAST(prod AS VARCHAR(MAX))='MONITOR' and CAST(quan as DECIMAL(10,4))<2 then 2 else CAST(quan as DECIMAL(10,4)) end as quan
from products_test;
Old answer: Please try this modified query :
select *,
case when CAST(prod AS VARCHAR(MAX))='CPU' and quan>1000 then 1000
when CAST(prod AS VARCHAR(MAX))='MOUSE' and quan>1024 then 1024
when CAST(prod AS VARCHAR(MAX))='MONITOR' and quan<2 then 2 else quan end as quan
from products_test;
if this works successfully, the Prod is in fact defined as int and
you can never get the then (true case) values in CASE statements.
You probably need to compare codes or foreign keys from master table which has values of 'CPU', 'MOUSE' and 'MONITOR' with prod.