Please i need to write somo querys fron only ONE TABLE

Hellio,

1. Develop the SQL script or pseudocode that lists all the people whose father and mother were born on the same day.

SELECT p.rut, p.FullName
FROM tPersona p
JOIN tPersona padre With(Nolock) ON p.rutPadre = padre.rut
JOIN tPersona madre With(Nolock) ON p.rutMadre = madre.rut
WHERE padre.Birthdate IS NOT NULL 
  AND madre.Birthdate IS NOT NULL
  AND padre.Birthdate = madre.Birthdate;

2. List the name of people who have only one parent, father or mother alive.

SELECT p.rut, p.FullName
FROM tPersona p
LEFT JOIN tPersona padre With(Nolock) ON p.rutPadre = padre.rut
LEFT JOIN tPersona madre With(Nolock) ON p.rutMadre = madre.rut
WHERE (padre.live = TRUE AND (madre.live IS NULL OR madre.live = FALSE))
   OR (madre.live = TRUE AND (padre.live IS NULL OR padre.live = FALSE));

3. Update the rutPadre that points to a non-existent record.

UPDATE tPersona
SET rutPadre = NULL
WHERE rutPadre IS NOT NULL 
  AND rutPadre NOT IN (SELECT rut FROM tPersona);

Hope above query help to get your work done

List all people whose father and mother were born on the same day :

SELECT p.FullName
FROM tPersona p
JOIN tPersona padre ON p.rutPadre = padre.rut
JOIN tPersona madre ON p.rutMadre = madre.rut
WHERE padre.Birth = madre.Birth;

List the name of people who have only one parent, father or mother alive.

SELECT p.FullName
FROM tPersona p
LEFT JOIN tPersona padre ON p.rutPadre = padre.rut
LEFT JOIN tPersona madre ON p.rutMadre = madre.rut
WHERE (padre.live = TRUE AND madre.live IS NULL) 
   OR (madre.live = TRUE AND padre.live IS NULL)

Update the rutPadre that points to a non-existent record.

UPDATE tPersona
SET rutPadre = NULL
WHERE rutPadre IS NOT NULL
  AND rutPadre NOT IN (SELECT rut FROM tPersona)