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Databases

Posted by Yash Patel
Yash Patel
1,751 Points

DERIVED Subquery to find all Female customer sales data (under Challenge Task)

This is Challenge Task #4 for SQL Querying Relational Databases

SELECT * FROM Sale AS s 
    INNER JOIN (SELECT * FROM Customer WHERE Customer.Gender = "F") 
        AS f 
            ON s.CustomerID = f.CustomerID;

What am I doing wrong?

Joshua Hardy
Joshua Hardy
17,317 Points

Do you have a link to the task?

Yash Patel
Yash Patel
1,751 Points

@Joshua Hardy https://teamtreehouse.com/library/querying-relational-databases/subqueries/subqueries

4 Answers

Joshua Hardy
Joshua Hardy
17,317 Points
Joshua Hardy
Joshua Hardy
17,317 Points 
SELECT * FROM sale AS s
           INNER JOIN (SELECT customerid FROM customer WHERE gender = 'F') AS c
           ON s.customerid = c.customerid;

On the inner join, I am selecting customerid and you are selecting all.

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

This gets the right rows, but with much more data than expected.

The challenge is expecting your subquery to select only the customer ID's from the Customers table, not all the columns.

Yash Patel
Yash Patel
1,751 Points
Yash Patel
Yash Patel
1,751 Points

Changing that worked, thanks!

Can you clarify why having all the columns wouldn't work considering all the Males were filtered out?

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

That "Select all columns from the Sale table only." is your clue. Your current subquery would also give you every column from the Customers table, which is not what the challenge expected to see.

nolan emirot
nolan emirot
2,826 Points
nolan emirot
nolan emirot
2,826 Points

If we specify all the columns instead of "*" it won't work but it's correct...