set nocount on用法
SET NOCOUNT ON is a T-SQL statement used in Microsoft SQL Server to suppress the message indicating the number of rows affected by each Transact-SQL statement. By default, SQL Server returns the message indicating the number of rows affected by a statement. However, in certain scenarios, this message can be unnecessary and may negatively impact the performance of the application.
When SET NOCOUNT ON is used, SQL Server stops sending the message indicating the number of rows affected by each statement. This can be particularly useful when executing multiple statements or stored procedures that don't require this information.
To use SET NOCOUNT ON, you simply include the statement at the beginning of a batch, stored procedure, or trigger. Once it is set, SQL Server will not send the row count message for subsequent statements within that scope until SET NOCOUNT is turned off or the scope ends.
The primary benefit of using SET NOCOUNT ON is improved performance. Sending the row count message after each statement can add unnecessary overhead, especially when dealing with large datasets. Suppressing these messages can help reduce network traffic and improve the overall efficiency of the application.
It's important to note that SET NOCOUNT ON does not affect the actual execution or result set of the SQL statements; it only suppresses the row count messages. Therefore, it is safe to use this statement without affecting the functionality of the database operations.
However, it's worth mentioning that in some cases, the row count information can be valuable for troubleshooting or monitoring purposes. Therefore, it's important to carefully consider the implications before using SET NOCOUNT ON throughout an application.
Overall, SET NOCOUNT ON is a useful statement in SQL Server that can help improve performance by suppressing row count messages. It should be used judiciously, considering the specific requirements and performance considerations of each application.

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