Find a data throughout out other data mysql - mysql

Question

I've literally no idea how to find the "via" field from 'sede' table starting from the "cognome" field in 'impiegato' table.
CREATE TABLE IF NOT EXISTS `mydb`.`impiegato` (
`codice` VARCHAR(45) NOT NULL,
`cognome` VARCHAR(45),
`nomedipart` VARCHAR(45),
`sede` VARCHAR(45),
`data` VARCHAR(45),
PRIMARY KEY (`codice`))
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`sede`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`sede` (
`cittaSede` VARCHAR(45) NOT NULL,
`via` VARCHAR(45) NULL,
`cap` VARCHAR(45) NULL,
PRIMARY KEY (`cittaSede`))
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`dipartimento`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`dipartimento` (
`nome` VARCHAR(45) NOT NULL,
`cittaSede` VARCHAR(45) NOT NULL,
`Telefono` VARCHAR(45),
`codDirett` VARCHAR(45),
INDEX `fk_dipartimento_idx` (`codDirett` ASC),
PRIMARY KEY (`nome`),
INDEX `fk_sede_idx` (`cittaSede` ASC),
CONSTRAINT `fk_dipartimento`
FOREIGN KEY (`codDirett`)
REFERENCES `mydb`.`impiegato` (`codice`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `fk_sede`
FOREIGN KEY (`cittaSede`)
REFERENCES `mydb`.`sede` (`cittaSede`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`progetto`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`progetto` (
`nomeProgetto` VARCHAR(45) NOT NULL,
`budget` VARCHAR(45),
PRIMARY KEY (`nomeProgetto`))
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`partecipazione`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`partecipazione` (
`codImpieg` VARCHAR(45) NOT NULL,
`progetto` VARCHAR(45),
PRIMARY KEY (`codImpieg`),
INDEX `fk_progetto_idx` (`progetto` ASC),
CONSTRAINT `fk_impiegato`
FOREIGN KEY (`codImpieg`)
REFERENCES `mydb`.`impiegato` (`codice`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `fk_progetto`
FOREIGN KEY (`progetto`)
REFERENCES `mydb`.`progetto` (`nomeProgetto`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;

Answer 1

You have to match the impiegato row with the desired cognome with the row in sede with the same sede value, and that's what joins do:
select via
from sede s
join impiegato i
on s.sede = i.sede
where i.cognome = 'desiredCognome'