what is the use of sql code example

Example: SQL

CREATE TABLE friends (
   id INTEGER,
   name TEXT,
   birthday DATE
);

INSERT INTO friends (id, name, birthday) 
VALUES (1, 'Jane Doe', '1990-05-30');


INSERT INTO friends(id , name , birthday)
VALUES(2 , 'APOORV' , '2000-2-2');



UPDATE friends
SET name = 'Jane Srivastava'
WHERE id = 1;

ALTER TABLE friends 
ADD COLUMN email TEXT; 


UPDATE friends 
SET email =  '203029@klsafjls'
where id  = 1; 

UPDATE friends 
SET email =  '203029@klsafjls'
where id  = 2;

DELETE FROM friends 
WHERE id = 1;


SELECT * 
FROM friends;