How to fix ERROR 1302: Conflicting declarations in MySQL

MySQLINTERMEDIATEMEDIUMUpdated Dec 25, 2025· 118 views

Error 1302 occurs when a stored procedure or function has duplicate variable declarations or a local variable conflicts with a parameter name. Rename one of the conflicting identifiers to resolve the issue.

Quick fix

Fixes 1302

ERROR 1302: Conflicting declarations: 'name1' and 'name2'
  1. Identify the conflicting declarations
  2. Review your procedure parameters
  3. Find conflicting local variable names
  4. Rename the conflicting variable
mysql — error
ERROR 1302: Conflicting declarations: 'name1' and 'name2'
ERROR 1302: Conflicting declarations

What this error means

MySQL Error 1302 (ER_CONFLICTING_DECLARATIONS) indicates that your stored procedure, function, or trigger contains conflicting or duplicate declarations. This typically happens when you declare a local variable with the same name as a procedure parameter, or when you declare the same variable twice in different scopes. MySQL enforces strict naming to prevent ambiguity in variable scope resolution, so it rejects any SQL code with conflicting declarations to ensure your procedures execute predictably.

Typical symptoms

  • Stored procedure or function creation fails with "ERROR 1302: Conflicting declarations"
  • Trigger creation fails when declaring variables that conflict with column names or parameters
  • Local variable declaration conflicts with a parameter name of the same procedure
  • The same variable name is declared multiple times in overlapping scopes

Common causes

  1. Declaring a local variable with the same name as a procedure or function parameter
  2. Declaring the same variable name twice in the same or overlapping scope blocks
  3. Variable or parameter names that conflict with table column names in certain contexts
  4. Character set or collation declarations that conflict with each other in the same statement

How to fix "ERROR 1302: Conflicting declarations"

1Identify the conflicting declarations

Look at your error message carefully. The full error includes the conflicting names:

bash
ERROR 1302: Conflicting declarations: 'name1' and 'name2'

The error message will show you exactly which two identifiers are conflicting. This is your starting point for fixing the issue.

2Review your procedure parameters

Check the parameters defined in your CREATE PROCEDURE or CREATE FUNCTION statement. List all parameter names:

sql
CREATE PROCEDURE my_proc(
  IN param1 VARCHAR(100),
  IN param2 INT,
  OUT result VARCHAR(255)
)

Note down all parameter names so you can compare them against local variables.

3Find conflicting local variable names

Within the BEGIN...END block of your procedure, find all DECLARE statements:

sql
BEGIN
  DECLARE param1 VARCHAR(50);  -- PROBLEM: conflicts with input parameter
  DECLARE myVar INT;
  -- procedure code here
END

Look for any DECLARE statements that use the same name as a parameter or another DECLARE in the same block.

4Rename the conflicting variable

Choose one of the conflicting names and rename it to be unique. Typically, rename the local variable (DECLARE) rather than the parameter:

sql
CREATE PROCEDURE my_proc(
  IN param1 VARCHAR(100),
  IN param2 INT,
  OUT result VARCHAR(255)
)
BEGIN
  DECLARE param1_temp VARCHAR(50);  -- Renamed from param1
  DECLARE myVar INT;
  SET param1_temp = param1;  -- Use the renamed variable
  -- rest of procedure
END

Update all references to use the new variable name throughout the procedure.

5Use consistent naming conventions

Adopt a naming convention to prevent future conflicts. For example, prefix local variables:

sql
CREATE PROCEDURE process_user(
  IN userId INT,
  IN userName VARCHAR(100)
)
BEGIN
  DECLARE v_tempId INT;
  DECLARE v_tempName VARCHAR(100);
  DECLARE v_result VARCHAR(255);
  -- Use v_ prefix for all local variables
END

Common conventions include prefixes like v_ (variable), l_ (local), or suffixes like _temp or _var.

6Test the corrected procedure

After renaming, drop and recreate the procedure:

sql
DROP PROCEDURE IF EXISTS my_proc;

CREATE PROCEDURE my_proc(
  IN param1 VARCHAR(100),
  IN param2 INT,
  OUT result VARCHAR(255)
)
BEGIN
  DECLARE param1_temp VARCHAR(50);
  -- ... rest of code
END;

Then call it to verify it works:

sql
CALL my_proc('test', 123, @result);
SELECT @result;

Advanced notes

MySQL applies strict scoping rules for variables in stored procedures. Local variables in inner BEGIN...END blocks take precedence over parameters, which take precedence over table columns. This design prevents unexpected behavior, but means you cannot have name conflicts at any level. In some MySQL versions or with certain storage engines, character set and collation declarations can also trigger this error if incompatible specifications are used in the same statement. When migrating procedures from other databases (Oracle, SQL Server), be aware that their scoping rules may differ, so you may need to rename variables during migration.

Frequently asked questions

What does "1302" mean?
MySQL Error 1302 (ER_CONFLICTING_DECLARATIONS) indicates that your stored procedure, function, or trigger contains conflicting or duplicate declarations. This typically happens when you declare a local variable with the same name as a procedure parameter, or when you declare the same variable twice in different scopes. MySQL enforces strict naming to prevent ambiguity in variable scope resolution, so it rejects any SQL code with conflicting declarations to ensure your procedures execute predictably.
How do I fix "1302"?
Error 1302 occurs when a stored procedure or function has duplicate variable declarations or a local variable conflicts with a parameter name. Rename one of the conflicting identifiers to resolve the issue.
What causes "1302"?
Declaring a local variable with the same name as a procedure or function parameter Declaring the same variable name twice in the same or overlapping scope blocks Variable or parameter names that conflict with table column names in certain contexts
Is the "1302" error serious?
It is a medium-severity error — more of a blocker than a risk. The steps above resolve it.

Official resources & further reading