Checking @@ROWCOUNT failing

I have a code similar to the one below in one of my SQL procedures,

declare @rowcount int

update table1
set value = @value
where id = @id

select @rowcount = @@ROWCOUNT

 if ( @rowcount = 0 )
 begin
    insert into table1(id, value1,value2...)
    select (@id, @value1, @value2...)
 end

But it fails rarely, like once in a day etc. That means the data exists in the table and @@rowcount is 0 and it tried to insert data and primary key violation happening. Here all values which are inserting ie. id,value1,value2 etc are integers. Any thoughts?

I'm not sure why you're using a variable, but you need to protect multiple statements with a transaction. What's happening is two users are calling the procedure at the same time, both are getting rowcount = 0, and then they're both trying to insert as a result.

set transaction isolation level serializable;
begin transaction;

update dbo.table1
  set value = @value
  where id = @id;

if (@@ROWCOUNT = 0)
begin
  insert dbo.table1(id, value1,value2...)
    values(@id, @value1, @value2...);
end 

commit transaction;

I blogged about this since writing this answer:

• Please stop using this UPSERT anti-pattern

StackExchange Database Administrators Q#232558, answer score: 15