In sql query as follows

The problem occurs because you have two different data types returned from the case structure. The Head_Type is a bit and you're returning it in the else branch. In all other branches you're returning character data. Because there is no implicit conversion from bit to varchar you face the error

So to correct this you should explicitely convert the bit. Something like the following:

Select designation , 
       (Case 
           when Head_Type = '0' then 'Courseofficer'
           When Head_Type = '1' then 'Authorisedsignatory' 
           else cast(Head_Type as varchar) 
        end) as Type
from Designations

The next thing is that the field you compare is a bit. With bit you shouldn't use char comparison since it causes an extra conversion. So the case would be better with

Select designation , 
       (Case 
           when Head_Type = 0 then 'Courseofficer'
           When Head_Type = 1 then 'Authorisedsignatory' 
           else cast(Head_Type as varchar) 
        end) as Type
from Designations

since you're using just a single value comparison I would also simplify the case structure to

Select designation ,
       (Case Head_Type
           when 0 then 'Courseofficer'
           When 1 then 'Authorisedsignatory'
           else cast(Head_Type as varchar)
        end) as Type
from Designations

Also as Maciej Los[^] pointed out in the first solution, the condition for the case could be simplified to use the already existing data.


As a side note The else branch handles the situation that the head_type is possibly null so you may need to adjust the code to better handle such situation...

Select designation , Case when Head_Type = '0' then 'Courseofficer'
 When Head_Type = '1' then 'Authorisedsignatory' else Head_Type end as Type
from Designations

end as "type" mean.. the name of the "type" you seperated by end) as type
end as "des" mean column name will be des

Select designation , Case when Head_Type = '0' then 'Courseofficer'
 When Head_Type = '1' then 'Authorisedsignatory' else Head_Type end
from Designations

The second one make the output with any specified column name,It just show (No column name)
if u use bracket () mean stop with only end dont use..as requires column name

Select designation , (Case when Head_Type = '0' then 'Courseofficer'
 When Head_Type = '1' then 'Authorisedsignatory' else Head_Type end)
from Designations