MySQL Workbench Error 1005 cant create table - mysql

Question

So I am very new to MySQL but I would like to think I that grasp a decent bit of it so far. I am struggling with the creation of the table PROJECT. I'm almost positive after my own research that it has something to do with my keys in the table. But I do not understand where the problem is or how to fix it.
The SQL queries below creates all tables for the project. I'm not sure of the problem because I only get the error code for the project for now. Any insight and advice on what causes this and how to rectify this in the code would be greatly appreciated.
CREATE TABLE IF NOT EXISTS `ebrasi1db`.`employee` (
`ssn` VARCHAR(10) NOT NULL,
`fname` VARCHAR(45) NULL DEFAULT NULL,
`minit` VARCHAR(1) NULL DEFAULT NULL,
`lname` VARCHAR(45) NULL DEFAULT NULL,
`bdate` DATE NULL DEFAULT NULL,
`address` VARCHAR(45) NULL DEFAULT NULL,
`sex` VARCHAR(1) NULL DEFAULT NULL,
`salary` INT(11) NULL DEFAULT NULL,
`superssn` VARCHAR(10) NULL DEFAULT NULL,
`dno` INT(11) NULL DEFAULT NULL,
PRIMARY KEY (`ssn`),
INDEX `superssn_idx` (`superssn` ASC),
INDEX `dno_idx` (`dno` ASC),
CONSTRAINT `superssn`
FOREIGN KEY (`superssn`)
REFERENCES `ebrasi1db`.`employee` (`ssn`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `dno`
FOREIGN KEY (`dno`)
REFERENCES `ebrasi1db`.`department` (`dnumber`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `ebrasi1db`.`department`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `ebrasi1db`.`department` (
`dnumber` INT(11) NOT NULL,
`dname` VARCHAR(45) NULL DEFAULT NULL,
`mgrssn` VARCHAR(10) NULL DEFAULT NULL,
`mgrstartdate` DATE NULL DEFAULT NULL,
PRIMARY KEY (`dnumber`),
INDEX `mgrssn_idx` (`mgrssn` ASC),
CONSTRAINT `mgrssn`
FOREIGN KEY (`mgrssn`)
REFERENCES `ebrasi1db`.`employee` (`ssn`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `ebrasi1db`.`dept_locations`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `ebrasi1db`.`dept_locations` (
`dnumber` INT(11) NOT NULL,
`dlocation` VARCHAR(45) NOT NULL,
PRIMARY KEY (`dnumber`, `dlocation`),
CONSTRAINT `dnumber`
FOREIGN KEY (`dnumber`)
REFERENCES `ebrasi1db`.`department` (`dnumber`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `ebrasi1db`.`project`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `ebrasi1db`.`project` (
`pnumber` INT(11) NOT NULL,
`pname` VARCHAR(45) NULL,
`plocation` VARCHAR(45) NULL,
`dnum` INT(11) NOT NULL,
PRIMARY KEY (`pnumber`),
INDEX `dnum_idx` (`dnum` ASC),
INDEX `plocation_idx` (`plocation` ASC),
CONSTRAINT `dnum`
FOREIGN KEY (`dnum`)
REFERENCES `ebrasi1db`.`department` (`dnumber`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `plocation`
FOREIGN KEY (`plocation`)
REFERENCES `ebrasi1db`.`dept_locations` (`dlocation`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `ebrasi1db`.`works_on`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `ebrasi1db`.`works_on` (
`essn` VARCHAR(10) NOT NULL,
`pno` INT NOT NULL,
`hours` DECIMAL(5,2) NULL,
PRIMARY KEY (`essn`, `pno`),
INDEX `pno_idx` (`pno` ASC),
CONSTRAINT `works_on_essn`
FOREIGN KEY (`essn`)
REFERENCES `ebrasi1db`.`employee` (`ssn`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `pno`
FOREIGN KEY (`pno`)
REFERENCES `ebrasi1db`.`project` (`pnumber`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `ebrasi1db`.`dependent`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `ebrasi1db`.`dependent` (
`essn` VARCHAR(10) NOT NULL,
`dependent_name` VARCHAR(45) NOT NULL,
`sex` VARCHAR(1) NULL,
`bdate` DATE NULL,
`relation` VARCHAR(45) NULL,
PRIMARY KEY (`essn`, `dependent_name`),
CONSTRAINT `dependent_essn`
FOREIGN KEY (`essn`)
REFERENCES `ebrasi1db`.`employee` (`ssn`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;

Answer 1

Your problem lies essentially in the fact that you are trying to create a constraint to a non key column (because the referenced table has a double key).
In your table project you have:
CONSTRAINT `plocation`
FOREIGN KEY (`plocation`)
REFERENCES `dept_locations` (`dlocation`)
ON DELETE NO ACTION
ON UPDATE NO ACTION
dept_locations.dlocation is not a key ALONE (primary key), therefore the reason you are not able to create that constraint.
You need to make the constraint for both keys from the referenced table like this:
CONSTRAINT `plocation`
FOREIGN KEY (`pnumber`, `plocation`)
REFERENCES `dept_locations` (`dnumber`, `dlocation`)
ON DELETE NO ACTION
ON UPDATE NO ACTION
In this case you won't need the first constraint dnum as it is already referenced in dept_locations table.
Also note that you tables department and employee will not be created because one reference the other so you need to create the tables first without the constraints then apply the constraints like:
ALTER TABLE `employee` add
CONSTRAINT `dno`
FOREIGN KEY (`dno`)
REFERENCES `department` (`dnumber`)
ON DELETE NO ACTION
ON UPDATE NO ACTION;
Same for the department table and its constraint to employee

Answer 2

Normally you get the Error 1005 when it unable to create the foreign keys. When you are creating a foreign key constraint the parent table should be available in the database.
In your case 'employee' table has a FK to 'department' table but you are trying to create the 'employee' table before creating the 'department' table. Also the 'department' table has a FK back to 'employee' table. Therefore you are not able to create the 'department' table first. To solve this you may create the 'department' table first without FK to 'employee' table. Then create the 'employee' table and then alter the 'department' table with FK.
Here is the modified code for first two tables and follow the same pattern for rest if you get the same error.
CREATE TABLE IF NOT EXISTS `ebrasi1db`.`department` (
`dnumber` INT(11) NOT NULL,
`dname` VARCHAR(45) NULL DEFAULT NULL,
`mgrssn` VARCHAR(10) NULL DEFAULT NULL,
`mgrstartdate` DATE NULL DEFAULT NULL,
PRIMARY KEY (`dnumber`),
INDEX `mgrssn_idx` (`mgrssn` ASC))
ENGINE = InnoDB;
CREATE TABLE IF NOT EXISTS `ebrasi1db`.`employee` (
`ssn` VARCHAR(10) NOT NULL,
`fname` VARCHAR(45) NULL DEFAULT NULL,
`minit` VARCHAR(1) NULL DEFAULT NULL,
`lname` VARCHAR(45) NULL DEFAULT NULL,
`bdate` DATE NULL DEFAULT NULL,
`address` VARCHAR(45) NULL DEFAULT NULL,
`sex` VARCHAR(1) NULL DEFAULT NULL,
`salary` INT(11) NULL DEFAULT NULL,
`superssn` VARCHAR(10) NULL DEFAULT NULL,
`dno` INT(11) NULL DEFAULT NULL,
PRIMARY KEY (`ssn`),
INDEX `superssn_idx` (`superssn` ASC),
INDEX `dno_idx` (`dno` ASC),
CONSTRAINT `superssn`
FOREIGN KEY (`superssn`)
REFERENCES `ebrasi1db`.`employee` (`ssn`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `dno`
FOREIGN KEY (`dno`)
REFERENCES `ebrasi1db`.`department` (`dnumber`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
alter table department add
CONSTRAINT `mgrssn`
FOREIGN KEY (`mgrssn`)
REFERENCES `ebrasi1db`.`employee` (`ssn`)
ON DELETE NO ACTION
ON UPDATE NO ACTION;