MySQL – Error 1064 with Simple Query in MySQL Workbench

You will get this message if you're trying to add a constraint with a name that's already used somewhere else.

According to this post you can check your constraint like this:

If the table you're trying to create includes a foreign key constraint, and you've provided your own name for that constraint, remember that it must be unique within the database. Run this query to see if that name is in use somewhere:

SELECT
  constraint_name,
  table_name
FROM
  information_schema.table_constraints
WHERE
  constraint_type = 'FOREIGN KEY'
  AND table_schema = DATABASE()
ORDER BY
  constraint_name;

I see a few issues with your existing code to create the waiters table.

First, the index creation code is incorrect. The column to be indexed should be inside the parentheses -- INDEX (manager_id).

Second, you are trying to add an index on a column that is not listed in your waiters table. You need to include the manager_id as a column.

Third, the syntax for the FOREIGN KEY constraint is incorrect. The syntax is from the MySQL docs is:

[CONSTRAINT [symbol]] FOREIGN KEY
    [index_name] (index_col_name, ...)
    REFERENCES tbl_name (index_col_name,...)
    [ON DELETE reference_option]
    [ON UPDATE reference_option]

So your code should be:

CREATE  TABLE `waiters` (
  `waiter_id` INT NOT NULL AUTO_INCREMENT ,
  `name` VARCHAR(45) NOT NULL ,
  `password` VARCHAR(45) NOT NULL ,
  `manager_id` INT NOT NULL,
  PRIMARY KEY (`waiter_id`) ,
  INDEX  (`manager_id`) ,
  CONSTRAINT FK_Manager
    FOREIGN KEY (`manager_id`)
    REFERENCES `managers` (manager_id)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;

See SQL Fiddle with Demo