How to fix ERROR 1305: FUNCTION database.function doesn't exist in MySQL

Ensure you are connected to the correct database:

SELECT DATABASE();

If the result is NULL or shows a different database, switch to the correct one:

USE your_database;

Always include an explicit USE statement before calling functions in production scripts.

Query the information schema to verify the function exists:

SELECT ROUTINE_NAME, ROUTINE_TYPE FROM information_schema.ROUTINES 
WHERE ROUTINE_SCHEMA = "your_database";

Or use the MySQL shorthand:

SHOW FUNCTION STATUS WHERE Db = "your_database";

Note the exact spelling and case of the function name. If the function is not listed, it needs to be created.

The most common cause is a space between the function name and the opening parenthesis. MySQL interprets this as a syntax error.

Incorrect:

SELECT IFNULL (value, default_value) FROM table;
SELECT CONCAT (col1, col2) FROM table;

Correct:

SELECT IFNULL(value, default_value) FROM table;
SELECT CONCAT(col1, col2) FROM table;

Update all function calls to remove the space before the parenthesis.

If the function exists but error 1305 still occurs, try calling it with the full qualified name:

SELECT database.function_name(arguments) FROM table;

For example:

SELECT mydb.calculate_price(quantity, rate) FROM orders;

This ensures MySQL searches the correct database schema, bypassing any context confusion.

Confirm that you are calling a function in a SELECT statement, not a procedure. Procedures are called with CALL:

Function (returns a value, used in SELECT):

SELECT my_function(col1) FROM table;

Procedure (does not return a value, uses CALL):

CALL my_procedure(arg1, arg2);

If error 1305 mentions a procedure, switch to CALL syntax. If it mentions a function but you defined a procedure, recreate it as a function.

On Unix systems with lower_case_table_names=0, function names are case-sensitive. Check your MySQL configuration:

SHOW VARIABLES LIKE 'lower_case_table_names';

If it returns 0 (case-sensitive), ensure your function call matches the exact case used in the CREATE FUNCTION statement:

-- Created as:
CREATE FUNCTION CalculatePrice() ...

-- Must be called as:
SELECT CalculatePrice(...);

-- Not:
SELECT calculateprice(...);

On Windows (lower_case_table_names=1) and macOS (lower_case_table_names=2), function names are case-insensitive.

The current user may lack EXECUTE privilege on the function. Check permissions:

SELECT PRIVILEGE_TYPE FROM information_schema.ROLE_TABLE_GRANTS 
WHERE TABLE_NAME = "your_database";

Grant EXECUTE privilege if missing:

GRANT EXECUTE ON FUNCTION your_database.my_function TO "app_user"@"localhost";
FLUSH PRIVILEGES;

Verify the user can execute the function:

SELECT my_function(test_arg);

If the function does not exist, create it from your application source code or schema definition:

CREATE FUNCTION my_function(param1 INT) RETURNS INT
DETERMINISTIC
BEGIN
  RETURN param1 * 2;
END;

Include the DETERMINISTIC keyword for functions that return the same output for the same input. This enables MySQL to cache results.

After creating the function, verify it works:

SELECT my_function(5);

After fixing the function call, test it in the environment where error 1305 occurred:

USE your_database;
SELECT my_function(argument) FROM table LIMIT 1;

If using a connection pool or ORM (like Sequelize, SQLAlchemy), ensure the connection is established to the correct database before executing the query.

In application code:

// Node.js with mysql2
const result = await connection.query(
  "USE mydb; SELECT my_function(?) as result",
  [arg]
);