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THROW (Transact-SQL)

  • Článek

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric SQL database in Microsoft Fabric

Raises an exception and transfers execution to a CATCH block of a TRY...CATCH construct.

Transact-SQL syntax conventions

Syntax

THROW [ { error_number | @local_variable }
    , { message | @local_variable }
    , { state | @local_variable } ]
[ ; ]

Arguments

error_number

A constant or variable that represents the exception. The error_number argument is int, and must be greater than or equal to 50,000, and less than or equal to 2,147,483,647.

message

A string or variable that describes the exception. The message argument is nvarchar(2048).

state

A constant or variable between 0 and 255 that indicates the state to associate with the message. The state argument is tinyint.

Remarks

Use state to help you identify the source of an error in your stored procedure, trigger, or statement batch. For example, if you use the same message in multiple places, a unique state value can help you locate where the error occurred.

The statement before the THROW statement must be followed by the semicolon (;) statement terminator.

If a TRY...CATCH construct isn't available, the statement batch is terminated. The line number and procedure where the exception is raised are set. The severity is set to 16.

If the THROW statement is specified without parameters, it must appear inside a CATCH block. This causes the caught exception to be raised. Any error that occurs in a THROW statement causes the statement batch to be terminated.

% is a reserved character in the message text of a THROW statement and must be escaped. Double the % character to return % as part of the message text, for example 'The increase exceeded 15%% of the original value'.

Differences between RAISERROR and THROW

The following table lists differences between the RAISERROR and THROW statements.

RAISERROR statement THROW statement
If a msg_id is passed to RAISERROR, the ID must be defined in sys.messages. The error_number parameter doesn't have to be defined in sys.messages.
The msg_str parameter can contain printf formatting styles. The message parameter doesn't accept printf style formatting.
The severity parameter specifies the severity of the exception. There's no severity parameter. When THROW is used to initiate the exception, the severity is always set to 16. However, when THROW is used to rethrow an existing exception, the severity is set to that exception's severity level.
Doesn't honor SET XACT_ABORT. Transactions are rolled back if SET XACT_ABORT is ON.

Examples

A. Use THROW to raise an exception

The following example shows how to use the THROW statement to raise an exception.

THROW 51000, 'The record does not exist.', 1;

Here's the result set.

Msg 51000, Level 16, State 1, Line 1
The record does not exist.

B. Use THROW to raise an exception again

The following example shows how to use the THROW statement to raise the last thrown exception again.

USE tempdb;
GO
CREATE TABLE dbo.TestRethrow
(    ID INT PRIMARY KEY
);
BEGIN TRY
    INSERT dbo.TestRethrow(ID) VALUES(1);

--  Force error 2627, Violation of PRIMARY KEY constraint to be raised.
    INSERT dbo.TestRethrow(ID) VALUES(1);
END TRY
BEGIN CATCH

    PRINT 'In catch block.';
    THROW;
END CATCH;

Here's the result set.

In catch block.
Msg 2627, Level 14, State 1, Line 1
Violation of PRIMARY KEY constraint 'PK__TestReth__3214EC272E3BD7D3'. Cannot insert duplicate key in object 'dbo.TestRethrow'.
The statement has been terminated.

C. Use FORMATMESSAGE with THROW

The following example shows how to use the FORMATMESSAGE function with THROW to throw a customized error message. The example first creates a user-defined error message by using sp_addmessage. Because the THROW statement doesn't allow for substitution parameters in the message parameter in the way that RAISERROR does, the FORMATMESSAGE function is used to pass the three parameter values expected by error message 60000.

EXEC sys.sp_addmessage
    @msgnum = 60000,
    @severity = 16,
    @msgtext = N'This is a test message with one numeric parameter (%d), one string parameter (%s), and another string parameter (%s).',
    @lang = 'us_english';
GO

DECLARE @msg NVARCHAR(2048) = FORMATMESSAGE(60000, 500, N'First string', N'second string');

THROW 60000, @msg, 1;

Here's the result set.

Msg 60000, Level 16, State 1, Line 2
This is a test message with one numeric parameter (`500`), one string parameter (First string), and another string parameter (second string).

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