I can not put foreign key in PHPMYADMIN

Question

I have my bank already created in phpmyadmin, are two tables, payments and students. I have seen several tutorials and read various ways of how to put a foreign key (fk_alunos) id_students in my payments table , nothing works.

Table pagamentos

CREATE TABLE IF NOT EXISTS `horus`.`pagamentos` (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  `situacao_aluno` VARCHAR(100) NOT NULL,
  `validade_plano` VARCHAR(15) NOT NULL,
  `planos` VARCHAR(100) NOT NULL,
  `vencimento` VARCHAR(50) NOT NULL,
  `cpf_amigo` VARCHAR(50) NOT NULL,
  `forma_pagamento` VARCHAR(100) NOT NULL,
  `data_matricula` VARCHAR(20) NOT NULL,
  `numero_documento` VARCHAR(50) NOT NULL,
  `data_documento` VARCHAR(15) NOT NULL,
  `valor` VARCHAR(6) NOT NULL,
  `status` VARCHAR(100) NOT NULL,
  `status_mensalidade` VARCHAR(100) NOT NULL,
  `alunos_id` INT(11) NOT NULL )

Table alunos

CREATE TABLE IF NOT EXISTS `horus`.`alunos` (
 `id` INT(11) NOT NULL AUTO_INCREMENT,
 `nome` VARCHAR(100) NOT NULL,
 `cpf` VARCHAR(15) NOT NULL,
 `rg` VARCHAR(15) NOT NULL,
 `nascimento` VARCHAR(50) NOT NULL,
 `sexo` VARCHAR(100) NOT NULL,
 `fone` VARCHAR(15) NOT NULL,
 `email` VARCHAR(100) NOT NULL,
 `endereco` VARCHAR(100) NOT NULL,
 `bairro` VARCHAR(100) NOT NULL,
 `cep` VARCHAR(10) NOT NULL,
 `estado` VARCHAR(50) NOT NULL,
 `cidade` VARCHAR(100) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE INDEX `cpf` (`cpf` ASC),
  UNIQUE INDEX `rg` (`rg` ASC))
  ENGINE = InnoDB
 AUTO_INCREMENT = 2
 DEFAULT CHARACTER SET = latin1;

In the payments table I put another field being the id_alunos In the indexes of the payments table I added the name of the key fk_alunos, spine id_pagamentos.

After that, when I try to execute the code "ALTER TABLE pagamentos ADD CONSTRAINT fk_alunos FOREIGN KEY(id_alunos) REFERENCES alunos (id_alunos)", only brings me mistakes saying :

" #1452 - Cannot add or update a Child Row: a Foreign key Constraint fails (horus.#sql-32d0_181, CONSTRAINT id_alunos FOREIGN KEY (id_alunos) REFERENCES alunos (id_alunos)) "

I tried to make relationship model by Workbench to then import into phpmyadmin, but not even so the foreign key appears.

Answer 1

Simple: REFERENCES alunos (id_alunos) is incorrect because the table alunos does not have a column called id_alunos. I believe the right thing would be REFERENCES alunos (id).

Another detail is that you own alunos_id on your table payments while you reference the column id_alunos, that doesn’t exist at your FK.

Answer 2

Guys I managed to find the solution! Thank you all...

The mistake was because my phpmyadmin was not updated, not even the drawing of the foreign key appeared.... I ended up reassembling the payments table again by writing in SQL and mentioning the Foreign key right there!

Thank you all.