Database Programming
Sections 4 – Joins
Overview
 Oracle Proprietary
Joins (8i and
prior):





 SQL: 1999
Compliant Joins:
Cartesian Product
Equijoin
Non-equijoin
Outer join
Self join
Marge Hohly
Cross joins
Natural joins
Using clause
Full or two sided
outer joins
 Arbitrary join
conditions for outer
joins




2
Cross Join
 ANSI/ISO SQL: 1999 syntax for
achieving of a Cartesian product
 Syntax:
 SELECT *
FROM employees
CROSS JOIN departments;
 Last week:
SELECT *
FROM employees, departments;
Marge Hohly
3
Natural Join
 ANSI/ISO SQL: 1999 Join equivalent of
an equijoin
 Join on all common columns
ie. columns with same name and data
type
 SYNTAX:
SELECT field1, field2
FROM table1 NATURAL JOIN table2
WHERE fieldn = value;
Marge Hohly
4
Example 4.2.3
 SELECT event_id,
song_id,
cd_number
FROM
d_play_list_items
NATURAL JOIN
d_track_listings
WHERE event_id =
105;
Marge Hohly
5
Example Natural Join
 SELECT employee_id,
last_name, department_id,
location_id
FROM employees
NATURAL JOIN departments;
Marge Hohly
6
4.2.6.5
5. Use an equijoin between the DJs on
Demand database tables, d_songs
and d_types. Display the type code,
description and title. Limit the rows
returned to those type codes between
70 and 80.
Marge Hohly
7
Join Using
 ANSI/ISO SQL: 1999 join condition used to
join two tables on only one column
 Typically used where NATURAL JOIN cannot
be used because there are other common
columns with same name and different data
types
 No table name or alias can be used on the
referenced column anywhere in the
statement
Marge Hohly
8
Join Using
 SYNTAX:
SELECT field1, field2, field3
FROM table1
JOIN table2
USING(column name);
 Example:
SELECT e.employee_id, e.last_name,
d.location_id
FROM employees e
JOIN departments d
USING(department_id);
Marge Hohly
9
Example
 SELECT e.employee_id,
e.last_name,
d.location_id
FROM employees e
JOIN departments d
USING(department_id);
Marge Hohly
10
JOIN ON


ANSI/ISO: 1999 join clause that may be used to specify the
condition or columns used:
Syntax:
SELECT field1, field2, field3
FROM table1 JOIN table2
ON(table1.fieldx=table2.fieldy);
SELECT e.last_name emp, m.last_name mgr
FROM employees e JOIN employees m
ON(e.manager_id = m.employee_id);

SELECT e.last_name as "EMP", w.last_name as "MGR“
FROM employees e JOIN employees w
ON (e.manager_id = w.employee_id)
WHERE e.last_name like 'H%';
Where clause can limit results.
Marge Hohly
11
Example of JOIN ON
 SELECT e.last_name,
e.department_id,
d.department_name
FROM employees e
JOIN departments d
ON (e.department_id
= d.department_id);
Marge Hohly
12
Summary/Comparison
Marge Hohly
13
Examples 4.3.6-8
2. Join DJs on Demand d_play_list_items,
d_track_listings, and d_cds tables with the JOIN
USING syntax. Include the song ID, CD number, title,
and comments in the output.
3. Display the city, department name, location ID, and
department ID for departments 10, 20, and 30 for the
city of Seattle.
6. Display job title, employee first name, last name, and
email for all employees that are stock clerks.
9. (Use Join On)
Query and display manager ID, department ID,
department name, first name, and last name for all
employees in departments 80, 90, 110, and 190.
Marge Hohly
14
Three-way Joins with the ON clause
 A three-way join is the join of three tables
 Syntax:
SELECT employee_id, city,
department_name
FROM employees e
JOIN departments d
ON (d.department_id = e.department_id)
JOIN locations l
ON (d.location_id=l.location_id);
Marge Hohly
15
Example
 SELECT employee_id, city,
department_name
FROM employees e
JOIN departments d
ON (d.department_id =
e.department_id)
JOIN locations l
ON
(d.location_id=l.location_id);
Marge Hohly
16
Revised example
 SELECT
e.employee_id, l.city,
d.department_name
FROM employees e,
departments d,
locations l
WHERE
e.department_id =
d.department_id
AND d.location_id =
l.location_id
Marge Hohly
17
INNER JOINS
 An inner join returns only those rows
that match the join condition
SELECT e.last_name, e.department_id,
d.department_name
FROM employees e
JOIN departments d
ON (e.department_id = d.department_id);
Marge Hohly
18
OUTER JOIN
 Outer joins return those rows that
match the join condition and those
that do not
 There are three ANSI/ISO SQL: 1999
outer joins:
 LEFT OUTER JOIN
 RIGHT OUTER JOIN
 FULL OUTER JOIN
Marge Hohly
19
LEFT OUTER JOIN

SELECT e.last_name, e.department_id, d.department_name
FROM employees e
LEFT OUTER JOIN departments d
ON(e.department_id=d.department_id);
 SQL 99 equivalent:
SELECT e.last_name, e.department_id,
d.department_name
FROM employees e, departments d
WHERE e.department_id=d.department_id(+);
 This statement will return those employees who do not
have a department_id
Marge Hohly
20
RIGHT OUTER JOIN

SELECT field1, field2 ....
FROM table1 a
RIGHT OUTER JOIN table2 b
ON (a.field=b.field);
or USING(field name);

SELECT e.last_name, e.department_id,
d.department_name
FROM employees e
RIGHT OUTER JOIN departments d
ON(e.department_id=d.department_id);

This statement will return those departments who do
not have any employees in them
Marge Hohly
21
FULL OUTER JOIN
 The FULL OUTER JOIN returns both matched and all
unmatched rows
 Syntax:
SELECT field1, field2, field3
FROM table1 a
FULL OUTER JOIN table2 b
ON a.field=b.field;
SELECT e.last_name, e.department_id,
d.department_name
FROM employees e
FULL OUTER JOIN departments d
ON(e.department_id=d.department_id);
 There is no direct comparable Oracle specific join
Marge Hohly
22
Example 4.4.5
 Construct a join to display a list of Global
Fast Foods customers whether or not they
have placed an order as yet and all the
customers who have placed orders.
 SELECT c.first_name, c.last_name,
o.order_number,o.order_date, o.order_total
FROM f_customers c
LEFT OUTER JOIN f_orders o
ON (c.id = o.cust_id);
Marge Hohly
23
Types of Joins
 Oracle Proprietary
Joins (8i and
prior):





 SQL: 1999
Compliant Joins:
Cartesian Product
Equijoin
Non-equijoin
Outer join
Self join
Marge Hohly
Cross joins
Natural joins
Using clause
Full or two sided
outer joins
 Arbitrary join
conditions for outer
joins




24