Error converting data type varchar to bigint. when using update - sql

Question

I'm using SQL Server. I'm trying to run the following SQL script and I'm getting this error:
Error converting data type varchar to bigint.
This is the script:
with T as
(
select
sp.ProfileId
,sp.ProfileHandle
,sp.[Description]
from
[SocialProfile] sp
inner join
Entity e on sp.EntityId = e.EntityId
where
e.EntityStatusId != 3 and e.EntityStatusId != 4
and sp.SocialProfileTypeId in (1, 2, 10)
and (ISNUMERIC(sp.ProfileHandle) = 1)
and IsRemoved = 0
)
update T
set ProfileHandle = NULL
where ProfileHandle = ProfileId
I tried to use cast function but it doesn't work. Can someone tell me what I'm doing wrong?

Answer 1

The isnumeric() doesn't give the protection you want. Use try_convert() for the comparison:
with T as (
select sp.ProfileId, sp.ProfileHandle, sp.[Description]
from [SocialProfile] sp inner join
Entity e
on sp.EntityId = e.EntityId
where e.EntityStatusId not in (3, 4) and
sp.SocialProfileTypeId in (1, 2, 10) and
ISNUMERIC(sp.ProfileHandle) = 1 and -- you can leave it in
IsRemoved = 0
)
update T
set ProfileHandle = NULL
where try_convert(int, ProfileHandle) = ProfileId;
SQL Server has a "feature" where it will rearrange the conditions in the query. The CTE does not get executed "first", so the isnumeric() is not necessarily run before the conversion in the where. I consider this a bug. Microsoft considers this a feature (because it provides more options for optimization).
The only ordering guaranteed in a query is through case expressions. The simplest work-around is try_convert().
In addition, I strongly recommend never relying on implicit conversions. Always explicitly convert. I have spent many hours debugging code for problems caused by implicit conversion.