当isnull（'sdas'，0）= 0时选择大小写，然后'hi'否则'bye'结尾为'Value'

Question

The below query

select case when isnull('23',0)=0 then 'hi' else 'bye' end as 'Value'

returns bye

BUT

select case when isnull('sdas',0)=0 then 'hi' else 'bye' end as 'Value'

returns the following Error message in MS-SqlServer2008R2

Msg 245, Level 16, State 1, Line 1
Conversion failed when converting the varchar value 'sdas' to data type int.

Can you clarify it on which stage it gets conversion has been done

Answer 1

'23' can be converted to int on the fly, but 'sdas' don't. take string(varchar)-type for all variables:

select case when isnull('sdas','0')='0' then 'hi' else 'bye' end as 'Value'

Answer 2

The problem is converting sdas to an integer 0 . Instead of using the isnull function, you could use the is null operator:

select case when 'sdas' is null then 'hi' else 'bye' end as 'Value'