I can't understand how use(.) in sql statements

Question

Student (student_id, student_name, year, GPA)
Course (course_id, course_name, credits, dept_id )
Enroll (student_id, course_id, mark, grade)

SELECT stu.student_name FROM Student AS stu, Enroll AS enr
WHERE stu.student_id = enr.student_id AND enr.course_id = "SCS1008" AND enr.mark < 80
ORDER BY stu.student_name;

There use Stu.Student_name.

I want to know from where the stu has come and without any attribute as stu, how to use it.

*Never* use commas in the `FROM` clause. *Always* use proper, explicit `JOIN` syntax. — Gordon Linoff, Nov 08 '17 at 12:54
Which DBMS are you using? `enr.course_id = "SCS1008"` is invalid standard SQL — , Nov 08 '17 at 13:04
Regrading Gordon's comment. Implicit vs explicit join can be seen here : https://stackoverflow.com/questions/44917/explicit-vs-implicit-sql-joins — ganit44, Jul 18 '18 at 04:57

score 1 · Accepted Answer · answered Nov 08 '17 at 12:54

1

It's an alias for the Student table, by virtue of Student AS stu. The alias stu allows you to reference the Student table by using a shortened name elsewhere in the query. It is short for Student.Student_Name, that being the Student_Name field on the Student table.

answered Nov 08 '17 at 12:54

cf_en

1,661
1
10
18

It is worth to mention, that aliases become a necessity when you have to join a table to itself. Aliases in this case allows you to distinguish between the two instances of the same table. – Pred Nov 08 '17 at 12:56

I can't understand how use(.) in sql statements

1 Answers1