分享raise用法归纳。

raise是一个Python内置函数，用于抛出异常。它可以接受多个参数，包括异常类型、异常值和追踪信息。raise还可以与break、continue等语句配合使用，控制循环流程。

raiserror用法有哪些

在SQL Server中，RAISEERROR是一个非常有用的内置函数，用于向客户端发送错误消息，通过使用RAISEERROR,我们可以在执行过程中遇到错误时通知用户，从而提高应用程序的可靠性，本文将详细介绍raiserror的用法，并在最后提供一个相关问题与解答的栏目，以帮助读者更好地理解这个函数。

RAISEERROR的基本语法

RAISEERROR函数的语法如下：

RAISEERROR ( message[, error_number[, severity[, state] ] ] )

message:要发送给客户端的错误消息。

error_number:可选参数，表示错误编号，如果不提供，系统将自动生成一个唯一的错误编号。

severity:可选参数，表示错误的严重程度，可以是1(Message)、2(Warning)、3(Critical)或4(Event)，默认值为1。

state:可选参数，表示错误状态，可以是0(Normal)或1(Invalid)，默认值为0。

RAISEERROR的使用场景

1、检查约束冲突：在插入或更新数据时，可以使用RAISEERROR检查约束冲突，例如主键约束、唯一约束等。

DECLARE @i INT = 1;
WHILE @i <= 100
BEGIN
    INSERT INTO Employees (EmployeeID, FirstName, LastName) VALUES (@i, 'John' + CAST(@i AS VARCHAR), 'Doe' + CAST(@i AS VARCHAR));
    SET @i = @i + 1;
    IF EXISTS (SELECT * FROM Employees WHERE EmployeeID = @i) RAISERROR ('Duplicate employee ID %d', 16, 1, @i);
END;

2、处理用户输入的数据类型错误：在处理用户输入的数据时，可以使用RAISEERROR检查数据类型是否正确，例如检查用户输入的日期是否有效等。

DECLARE @inputDate DATE;
SET @inputDate = '2022-13-01'; -无效的日期格式
IF NOT ISDATE(@inputDate) RAISERROR ('Invalid date format. Please enter a valid date in the format YYYY-MM-DD.', 16, 1);

3、在存储过程或函数中使用RAISEERROR:在自定义的存储过程或函数中，可以使用RAISEERROR向客户端发送错误消息。

CREATE PROCEDURE TestErrorHandling @InputValue INT AS
BEGIN
    IF @InputValue < 0 THEN
        RAISEERROR ('Negative input value %d is not allowed.', 16, 1, @InputValue);
    END IF;
END;

相关问题与解答

1、如何查看RAISEERROR生成的错误消息？

答：当RAISEERROR函数发送错误消息时，客户端会收到一条错误消息，如果客户端没有正确处理这些错误消息，可能会导致应用程序崩溃，建议在开发过程中开启SQL Server的错误报告功能，以便查看和分析RAISEERROR生成的错误消息，在SQL Server Management Studio中，可以通过以下步骤启用错误报告功能：工具 -> 选项 -> 查询 -> SQL Server错误报告，还可以使用以下T-SQL命令启用错误报告功能：sp_configure ‘show advanced options’, 1; RECONFIGURE; sp_configure ‘error reporting’, 1; RECONFIGURE; sp_configure ‘extended event logging’, 1; RECONFIGURE; sp_configure ‘diagnostics’, 1; RECONFIGURE; sp_configure ‘profiler enabled’, 1; RECONFIGURE; sp_configure ‘query performance profiling enabled’, 1; RECONFIGURE; sp_configure ‘dynamic management views (DMVs) enabled’, 1; RECONFIGURE; sp_configure ‘max server memory (in MB)’, MAXSERVERMEMORY; RECONFIGURE; sp_configure ‘memory protection’, ON; RECONFIGURE; sp_configure ‘auto update statistics turned on’, ON; RECONFIGURE; sp_configure ‘merge update added to buffer pool’, ON; RECONFIGURE; sp_configure ‘query hint execution increased to maximum’, ON; RECONFIGURE; sp_configure ‘query cache size increased to maximum’, ON; RECONFIGURE; sp_configure ‘force database query optimization on’, ON; RECONFIGURE; sp_configure ‘use of parallelism for background tasks increased to maximum’, ON; RECONFIGURE; sp_configure ‘use of parallelism for foreground tasks set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for system tasks set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for plan cache set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for index build set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for index rebuild set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for index usage set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for index maintenance set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for table scans set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for table updates set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for table deletes set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for table inserts set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for data reads set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for data writes set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for schema changes set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for permissions changes set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for backup and restore set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for log writes set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for high availability set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for distributed transactions set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for long running operations set to user level’, ON; RECONFIGURE; sp_configure ‘use of parallelism for blocking operations set to user level’, ON; RECONFRAMEWORK.dbo.sysmessages RAISERROR (N’A client error has occurred. For more information about this error follow the link in the error message.’,’258′); -SQLSTATE[22005]: [Microsoft][ODBC Driver][SQL Server]Invalid column name ”RAISERROR (N’A client error has occurred. For more information about this error follow the link in the error message.’,’258′); -SQLSTATE[22005]: [Microsoft][ODBC Driver][SQL Server]Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”RAISERROR (N”’Invalid column name ”’-End Error Message. END CATCH