MySQL 8.0

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SELECT VERSION();


VERSION()


8.0.25


DROP TABLE IF EXISTS `cliente`;

CREATE TABLE IF NOT EXISTS `cliente` (
  `id_cliente` INT NOT NULL AUTO_INCREMENT,
  `recomendacion` INT NOT NULL,
  PRIMARY KEY (`id_cliente`),
  FOREIGN KEY (`recomendacion`)
    REFERENCES `cliente` (`id_cliente`)
);
SET FOREIGN_KEY_CHECKS = 0;

INSERT INTO `cliente`
  (`id_cliente`, `recomendacion`)
VALUES
  (1, 2);

SET FOREIGN_KEY_CHECKS = 1;
SELECT
  `id_cliente`, `recomendacion`
FROM
  `cliente`;


id_cliente
recomendacion


1
2


INSERT INTO `cliente`
  (`id_cliente`, `recomendacion`)
VALUES
  (2, 3);
Cannot add or update a child row: a foreign key constraint fails (`db_829319697`.`cliente`, CONSTRAINT `cliente_ibfk_1` FOREIGN KEY (`recomendacion`) REFERENCES `cliente` (`id_cliente`))