sql server 的 @@rowcount 变量

@@rowcount

After each Transact-SQL statement, the server sets the value of this variable to the total number of records affected by it. It can be used to verify the success of selected operations:

     select Make, Model, EqTypeid
     into OldEquipment
     from Equipment
     where EqTypeid = 2

     if @@rowcount = 0
        Print "No rows were copied!"

Note

Certain statements (like the If statement) will set @@rowcount to 0, and certain statements (like Declare) will not affect it.

Rowcount_big() is a function introduced in SQL Server 2000. It returns the number of affected records in the form of a bigint number.

Tip

When you try to update an individual record, SQL Server will not report an error if your Where clause specifies a criterion that does not qualify any records. SQL Server will not update anything, and you might, for example, think that the operation was successful. You can use @@rowcount to identify such cases.

注意在select 和 @@rowcount 之间不要加任何语句，例如

    select top 1 @RatePlanID =  RatePlanID from RatePlan where CarrierID = @CustID and isInBound = @IsInBound
    if (@@rowcount = 0)

这两句之间如果加一句      select @sameRatePlanID=@RatePlanID

@@rowcount 会被影响到，导致对select的结果检查不对。