请问SQL语句中go有什么作用？

GO
Signals the end of a batch of Transact-SQL statements to the Microsoft® SQL Server™ utilities.

Syntax
GO

Remarks
GO is not a Transact-SQL statement; it is a command recognized by the osql and isql utilities and SQL Query Analyzer.

SQL Server utilities interpret GO as a signal that they should send the current batch of Transact-SQL statements to SQL Server. The current batch of statements is composed of all statements entered since the last GO, or since the start of the ad hoc session or script if this is the first GO. SQL Query Analyzer and the osql and isql command prompt utilities implement GO differently. For more information, see osql Utility, isql Utility, and SQL Query Analyzer. 

A Transact-SQL statement cannot occupy the same line as a GO command. However, the line can contain comments.

Users must follow the rules for batches. For example, any execution of a stored procedure after the first statement in a batch must include the EXECUTE keyword. The scope of local (user-defined) variables is limited to a batch, and cannot be referenced after a GO command.

USE pubs
GO
DECLARE @MyMsg VARCHAR(50)
SELECT @MyMsg = 'Hello, World.'
GO -- @MyMsg is not valid after this GO ends the batch.

-- Yields an error because @MyMsg not declared in this batch.
PRINT @MyMsg
GO

SELECT @@VERSION;
-- Yields an error: Must be EXEC sp_who if not first statement in 
-- batch.
sp_who
GO

SQL Server applications can send multiple Transact-SQL statements to SQL Server for execution as a batch. The statements in the batch are then compiled into a single execution plan. Programmers executing ad hoc statements in the SQL Server utilities, or building scripts of Transact-SQL statements to run through the SQL Server utilities, use GO to signal the end of a batch.

Applications based on the DB-Library, ODBC, or OLE DB APIs receive a syntax error if they attempt to execute a GO command. The SQL Server utilities never send a GO command to the server.

Permissions
GO is a utility command that requires no permissions. It can be executed by any user.

Examples
This example creates two batches. The first batch contains only a USE pubs statement to set the database context. The remaining statements use a local variable, so all local variable declarations must be grouped in a single batch. This is done by not having a GO command until after the last statement that references the variable.

USE pubs
GO
DECLARE @NmbrAuthors int
SELECT @NmbrAuthors = COUNT(*)
FROM authors
PRINT 'The number of authors as of ' +
      CAST(GETDATE() AS char(20)) + ' is ' +
      CAST(@NmbrAuthors AS char (10))
GO