why FROM if table name is specified

Question

I was wondering why need to specify FROM table if we already declared it before id?

Answer 1

Uchiha I supposed you refer to SQL sentence right? for example

SELECT name FROM students;

Obviously this is syntax for SQL but if you have two tables with a colum "name" each one, then, how could you do to get "name" from one specifically? with name of table.

Example:

Table1: Student
Field1: ID
Field2: Name
Field3: Phone
Field4: Age
Field5: Email

Table2: Teacher
Field1: ID
Field2: Name
Field3: Phone
Field4: Car
Field5: Address

So in that case, you must to know what information do you want

SELECT Name FROM Student;
You will show names of all students.

SELECT Name FROM Teacher;
You will show names of all teachers.

I will be hope you understand or maybe, if you have other problem or question, please, explain.

Answer 2

Ahh ok. That sintax is correct but you can use your query in this other way:

"SELECT username FROM users"

Other sintax are with my examples:

SELECT Student.Name, Student.Phone, Teacher.Name, Teacher.Phone FROM Student, Teacher;

With alias:

SELECT S.Name, S.Phone, T.Name, T.Phone FROM Student as S, Teacher as T;

Answer 3

Daniel I appreciate the effort you put in your answer.
I Guess a proper yet rude answer can be
*because that's how the syntax works*.
What I was really asking was why use

"SELECT users.username
from users"

(when you already specified the table next to username in the first line)
Thanks again.