SQL Server Error 134

Error number

134

Severity

15 (user-correctable error)

State

1

Product

Microsoft SQL Server Database Engine

Versions

All supported SQL Server versions (2016 to 2025), Azure SQL Database, Azure SQL Managed Instance

Category

Syntax & Object Resolution

Last reviewed

24 October 2026

What it means

Error 134 means the same @variable name is declared twice in one batch or one procedure, which T-SQL does not allow because a variable lives for the whole batch, not for the block it is declared in.

In T-SQL the scope of a local variable is the whole batch (or the whole body of a procedure, function or trigger) from the DECLARE onwards. BEGIN ... END, IF, ELSE and WHILE do not open a new scope, unlike in C# or Java. So two DECLAREs of the same name anywhere in one batch collide, even when one is inside a loop or a branch that would never run. The parser rejects the batch with 134 at severity 15 before any statement executes, and names the second declaration.

Procedure parameters count as declarations too, so DECLARE @rate in a procedure that already has a @rate parameter fails the same way. Splitting a script with GO ends the batch and its variables, which is why a duplicate name is fine across batches, and why the opposite mistake, using a variable after GO, raises error 137.

Common causes

• Two script snippets pasted into one batch, each with its own DECLARE @total.
• A DECLARE inside a WHILE loop or IF block for a name already declared earlier in the batch, on the assumption that blocks have their own scope.
• The same variable declared in both the IF and the ELSE branch.
• A procedure body that declares a variable with the same name as one of its parameters.
• Names that differ only in case, such as @Total and @TOTAL, on an instance with a case-insensitive collation.

Diagnose it

Read-only These queries only read metadata and dynamic management views. They do not change data, permissions or configuration, so they are safe to run first.

EXEC sp_describe_first_result_set
     N'DECLARE @total int = 0;
       SET @total = @total + 5;
       SELECT @total AS total;';

SELECT p.parameter_id, p.name AS parameter_name, TYPE_NAME(p.user_type_id) AS data_type
FROM sys.parameters AS p
WHERE p.object_id = OBJECT_ID(N'dbo.ApplyDiscount')
ORDER BY p.parameter_id;

How to fix it

Each fix is labelled with what it changes. Try read-only checks and the least invasive fix first, and test changes outside production.

DECLARE @i int = 1, @msg varchar(20);
WHILE @i <= 3
BEGIN
    SET @msg = 'row ' + CAST(@i AS varchar(5));   -- assign, do not redeclare
    PRINT @msg;
    SET @i += 1;
END;

DECLARE @order_total decimal(10,2) = 0;
DECLARE @invoice_total decimal(10,2) = 0;

DECLARE @total int = 0;
SELECT @total AS first_total;
GO
DECLARE @total int = 5;
SELECT @total AS second_total;

CREATE OR ALTER PROCEDURE dbo.ApplyDiscount
    @order_id int,
    @rate decimal(4,2) = NULL
AS
BEGIN
    SET @rate = ISNULL(@rate, 0.10);
    SELECT @order_id AS order_id, @rate AS rate;
END;

Examples

Two snippets pasted into one batch

DECLARE @total int = 0;
SELECT @total AS order_count;

DECLARE @total int = 5;   -- second snippet, same name
SELECT @total AS invoice_count;

Msg 134, Level 15, State 1, Line 4
The variable name '@total' has already been declared. Variable names must be unique within a query batch or stored procedure.

A DECLARE inside a loop for a name declared earlier

DECLARE @i int = 1;
DECLARE @msg varchar(20);
WHILE @i <= 3
BEGIN
    DECLARE @msg varchar(20) = 'row';   -- a loop is not a new scope
    SET @i += 1;
END;

Msg 134, Level 15, State 1, Line 5
The variable name '@msg' has already been declared. Variable names must be unique within a query batch or stored procedure.

A procedure that redeclares its own parameter

CREATE PROCEDURE dbo.ApplyDiscount @order_id int, @rate decimal(4,2)
AS
    DECLARE @rate decimal(4,2) = 0.10;   -- @rate is already a parameter
    SELECT @order_id AS order_id, @rate AS rate;

Msg 134, Level 15, State 1, Procedure ApplyDiscount, Line 3
The variable name '@rate' has already been declared. Variable names must be unique within a query batch or stored procedure.

How to prevent it

Declare all variables of a batch or procedure in one block at the top, with names that say what they hold. That makes duplicates obvious in review and avoids the loop trap: a DECLARE without a value inside a WHILE loop does not reset the variable on the next pass, so the old value leaks into the next iteration.

When you assemble scripts from several files, keep each file as its own batch ending in GO. For more on how batches, procedures and variables fit together, see stored procedures and functions.

Common questions

Learn more on CodeWithSQL

• Stored procedures and functions
• Advanced stored procedures
• SQL syntax guide

Official documentation

• DECLARE @local_variable (Transact-SQL)
• Variables (Transact-SQL)
• Database Engine events and errors 0 to 999

Last technically reviewed 24 October 2026; examples and diagnostics run on SQL Server 2025 (17.0.1145.4). Message text checked against the engine's sys.messages catalogue.