How to enforce a certain number or range of affected rows in SQL Server or ASP.NET C#

Question

for some SQL queries I know the expected number of rows that must be affected by UPDATE, DELETE or INSERT statements. It could be a number such as 1 or a range such as 0-1 or 1-2 etc.

What is the best way to enforce that this is the number of affected rows and that otherwise an exception is thrown?

Also, can I limit the number of rows affected for UPDATE/DELETE/INSERT to say 1 row and otherwise get an exception?

Thanks

Answer 1

For UPDATE, INSERT, and DELETE statements, ExecuteNonQuery returns the number of rows affected by the command.

I suggest you wrap the call in a transaction and if the result is not as expected rollback the transaction and throw an exception.

You can also use @@ROWCOUNT to do the same inside the query.

Answer 2

You can use TOP in insert, update and delete to enforce the number of rows affected. There is no exception thrown with this.

declare @T table (id int)

insert top(1) into @T values
(1),
(2),
(3)

If you want exception you can use @@ROWCOUNT in a transaction.

declare @Min int = 2
declare @Max int = 3

begin transaction

insert into Table1 values
(1),
(2),
(3),
(4)

if not @@rowcount between @Min and @Max
begin
  rollback
  -- Throw exception here, RAISERROR()
end
else
begin
  commit
end  

Answer 3

Use @@ROWCOUNT directly after your statement. If not equal to what you want, use RAISERROR.

One small warning however, RAISERROR has a severity parameter. Use a number between 11 and 19. Lower then 11 is considered a warning. Higher than 19 can only be done by sysadmins, is a fatal error and terminates your connection.

Answer 4

I think at the query level, the thing to use is either @@ROWCOUNT within the procedure or similar outside, but you need to use transactions.

If you want to go a little lower in the database (since the above technique would only protect queries designed to use such a framework), then you can use triggers on tables and get a count of the INSERTED or DELETED pseudo-tables and use RAISERRROR to raise an appropriate error.