SQL queries - For Customer and Sale representative - sql

Question

Q: List the numbers and names of all customers who are represented by Ann Hull but who do not currently have orders on file.
This is what I have so far... but it isn't the right output:
CREATE TABLE REP (
REP_NUM char(2) PRIMARY KEY,
LAST_NAME char(15),
FIRST_NAME char(15),
STREET char(15),
CITY char(15),
PROVINCE char(3),
ZIP char(5),
COMMISSION decimal(7, 2),
RATE decimal(3, 2)
);
CREATE TABLE CUSTOMER (
CUSTOMER_NUM char(3) PRIMARY KEY,
CUSTOMER_NAME char(35) NOT NULL,
STREET char(15),
CITY char(15),
PROVINCE char(3),
ZIP char(5),
BALANCE decimal(8, 2),
CREDIT_LIMIT decimal(8, 2),
REP_NUM char(2)
);
CREATE TABLE ORDERS (
ORDER_NUM char(5) PRIMARY KEY,
ORDER_DATE date,
CUSTOMER_NUM char(3)
);
CREATE TABLE PART (
PART_NUM char(4) PRIMARY KEY,
DESCRIPTION char(15),
ON_HAND decimal(4, 0),
CLASS char(2),
WAREHOUSE char(1),
PRICE decimal(6, 2)
);
CREATE TABLE ORDER_LINE (
ORDER_NUM char(5),
PART_NUM char(4),
NUM_ORDERED decimal(3, 0),
QUOTED_PRICE decimal(6, 2),
PRIMARY KEY (ORDER_NUM, PART_NUM)
);

Answer 1

SELECT * FROM CUSTOMER c
LEFT JOIN REP r
ON c.REP_NUM = r.REP_NUM
LEFT JOIN ORDERS o
ON o.CUSTOMER_NUM = c.CUSTOMER_NUM
WHERE o.CUSTOMER_NUM ISNULL
AND r.FIRST_NAME = 'Ann Hull'
Hope the above helps, It should work with minor modifications to the where clause especially combining the first and last names.

Answer 2

Filter the Rep table on firstname and lastname for Ann Hull and join it with the Rep table on the rep_num fields. To only return customers with no orders use a subquery to check that no orders exists (NOT EXISTS) in the Order table for a customer.
SELECT * FROM CUSTOMER c
JOIN REP r
ON c.REP_NUM = r.REP_NUM
AND r.FIRSTNAME = 'Ann'
AND r.LASTNAME = 'Hull'
AND NOT EXISTS(SELECT * FROM ORDERS o WHERE o.CUSTOMER_NUM = c.CUSTOMER_NUM)