Question

I am revising for my exam and I am a bit struggling with SQL queries..

Task for me is:

write a SQL query to list the full names of all the clients that
attend Allen Moore‟s classes, in alphabetical order of surname (i.e.
Lname column)

Client

Cid Fname Lname Fitness
C129 Julie Summer 1
C525 Max Hedrum 3
C628 John Long 3
C772 Warren Peace 2
C829 Anna Heart 2

Programme

Code Title Fitness
AR02 Aerobics 2
EN99 Endurance 3
TU10 Tune-Up 1
UB01 Upper-Body 2
YG02 Yoga 1

Staff

Sid Fname Lname Position Salary
S09 Jenny Sayer Psychologist 23500
S22 Allen Moore Instructor 21500
S28 Polly Purves Instructor 19000
S35 Jim Shoe Instructor 18000
S55 Mark Spencer Manager 25500

Class

Code Sid Cid
AR02 S35 C772
EN99 S22 C525
TU10 S35 C129
UB01 S28 C628
YG02 S22 C829
YG02 S22 C12

Is it something like:

SELECT Cliente.Fname, Cliente.Lname
FROM Staff, Class, Cliente
WHERE  Staff.Sid = Class.Sid AND Staff.Fname = "Allen" AND Staff.Lname = "Moore 
AND Class.Cid = Cliente.Cid
GROUP BY Cliente.lName ASC;

Thanks!

Answer 1

The GROUP BY in your query has to go, you don’t have to aggregate anything. I would prefer the SQL92 syntax for a join:

SELECT 
    Client.Fname, Client.Lname
FROM 
   Staff
INNER JOIN
Class ON Staff.Sid = Class.Sid AND Staff.Fname = "Allen" AND Staff.Lname = "Moore"
INNER JOIN 
Client ON Class.Cid = Cliente.Cid
ORDER BY Cliente.lName ASC;