Со3дал такую таблицу:
Create table table_workers(id serial primary key,name character(256) unique,position character(64));
CREATE TABLE table_tasks(id serial primary key,task character(1024),parent_task integer,executor character(256),date_death_line date,date_start date,status character(64),foreign key (parent_task) references table_tasks(id),foreign key (executor) references table_workers(name));
Insert into table_workers values(1,'Ivanov Ivan Ivanovich','Developer');
Insert into table_tasks values(1,'Добавить личный кабинет на сайт',NULL,'Ivanov Ivan Ivanovich','2020-05-01','2020-04-19','Назначено');
Выхлоп такой: