SQL302 Intermediate SQL Course - Workshop 2. Covers cast, convert and case, intermediate joins, rollup, cube, union, except, intersect and window functions.

1. SQL302
Intermediate SQL Programming
Based on SQL Clearly Explained by Jan Harrington and Microsoft SQL Server T-
SQL Fundamentals by Itzki Ben-gan
Workshop 2 – Joins, Set Operations, Window
Functions
Bookstore SQL302 Module 2 1

2. Note on SQL302 Slides
• These slides were originally designed to support a
single SQL course which was used for any of MS
Access, MySQL, Oracle and SQL Server.
• As such you may see here slides developed in any
one of the above products.
• We are in the process of migrating the Oracle,
Access, and MySQL slides out into their own slide
sets. The SQL302 slides will cover Microsoft SQL
Server.
Bookstore SQL302 Module 2 2

3. Warning!
• Below are some table name changes to be
aware of in doing queries. We have created
synonyms so either name should work.
New Name Old Name
Orders Order_filled
Order_Lines Orderlines
Bookstore SQL302 Module 2 3

4. SQL302 Contact Information
P.O. Box 6142
Laguna Niguel, CA 92607
949-489-1472
http://www.d2associates.com
slides.1@dhdursoassociates.com
Copyright 2001-2012All rights reserved.
Bookstore SQL302 Module 2 4

5. SQL302 Resources
• Bookstore database scripts found on
box.net at
http://tinyurl.com/SQLScripts
• Slides can be viewed on SlideShare…
http://www.slideshare.net/OCDatabases
• Follow up questions?
sql.support@dhdursoassociates.com
Bookstore SQL302 Module 2 5

6. Relational Database with constraints (from text)
Bookstore SQL302 Module 2 6

7. Sample Employees Database
Bookstore2 & SQL204 Module 1 7
Employees

8. More conventions
• Names can be surrounded with “ “ or [ ] as
in [order details].
• Some of the PowerPoint slides may have
this convention.
• Better practice is to use an underscore as in
order_details.
Bookstore SQL302 Module 2 8

9. SQL302
SQL Programming
Part 1 – Joins: Natural, Self and Outer
Bookstore SQL302 Module 2 9

10. Joins
• Inner (Covered in SQL202 course)
• Natural Join
• Self
• Data Warehouse operators
• Outer
– Left
– Right
– Full
• Cross
• Theta
• We will cover some of the more advanced or subtle
aspects of joins in this class
Bookstore SQL302 Module 2 10

11. Natural Joins
• Table1 natural join table3 – automatically
uses columns with same name
• Table 1 natural join table2 using(<column-
list>
• Not yet available in SQL Server
Bookstore SQL302 Module 2 11

12. Correlation Names (Table Aliases)
• Can abbreviate references to tables
• For example:
Select e.name, j.payrange
From employees as e
Inner join job_information as j
On e.jobcode = j.jobcode;
Bookstore SQL302 Module 2 12

13. Self Joins
• Implements a recursive relationship
• Important in various applications
– Parts lists/assemblies
– HR
– Etc.
– Table joined to itself using correlation names
Bookstore SQL302 Module 2 13

14. Self Joins
SELECT e.*, m.name
FROM employees AS e, employees
AS m
WHERE e.managerid =
m.employeeid;
Bookstore SQL302 Module 2 14

15. Bookstore SQL302 Module 2 15

16. Datawarehouse clauses
• Two keywords that can be added to a
grouped query
– Rollup
– Cube
• Places additional summary rows in the
result set
• Result set is a true relational result set
Bookstore SQL302 Module 2 16

17. Rollup
• Example: calculate average salaries by
job_title_code and manager
Bookstore SQL302 Module 2 17

18. Rollup results
Bookstore SQL302 Module 2 18

19. cube
• Similar to rollup but computes summary
rows in all dimensions
Bookstore SQL302 Module 2 19

20. Cube results
• Add a new set of rows which total by year
Bookstore SQL302 Module 2 20

21. Bookstore SQL302 Module 2 21

22. Outer Joins
• Left – selects all rows from the left or first table,
even if no match exists in the other table
– Widely used in commercial practice
– Especially useful for reporting
– Can be slower and interfere with optimizer
• Right – same idea but all rows from right table
• Full – all rows form both tables
Bookstore SQL302 Module 2 22

23. Left Outer Join
Basic SQL 92 Syntax:
Select <column-list>
From <table1>
Left join <table2>
On <join condition>
Bookstore SQL302 Module 2 23

24. Left Outer Join
• List all customers with their orders
• Include customers with no orders as well
Bookstore SQL302 Module 2 24

25. Left-Join
Basic Example:
SELECT customer_first_name,
customer_street, order_numb,
order_date
from customers as c
left join orders as o
on c.customer_numb =
o.customer_numb
Bookstore SQL302 Module 2 25

26. Left Join with Results
Bookstore SQL302 Module 2 26

27. Negative Left Join
• List all the customers who have not placed
any orders
• This is an example of a query which finds
unmatched records
Bookstore SQL302 Module 2 27

28. Negative Left-Join (Unmatched)
Basic Example:
SELECT customer_first_name,
customer_last_name, order_numb,
order_date
from customers as c
left join orders as o
on c.customer_numb =
o.customer_numb
Where order_numb is null;
Bookstore SQL302 Module 2 28

29. Bookstore SQL302 Module 2 29

30. Left Join w/ Partial Match
• List all customers along with any orders
placed in 1999
• If they did not place 1999 orders we still
want to include them in the printout
Bookstore SQL302 Module 2 30

31. Left Join w/ Partial Match
Example:
SELECT customer_first_name,
customer_last_name, order_numb, order_date
from customers as c
Left join
(select customer_numb, order_numb,
order_date
From orders
Where year(order_date) = 1999) as d
on c.customer_numb = d.customer_numb;
Bookstore SQL302 Module 2 31

32. Own Your Own
• List all books and their order totals for
1999
• Show the book even if there were no
orders placed in 1999
Bookstore SQL302 Module 2 32

33. Theta Joins
• Theta joins involve inequalities in the
matching conditions
• Can be used for some interesting queries
which do not involve the usual primary
key to foreign key matchings
Bookstore SQL302 Module 2 33

34. Theta join
• Find all customers that live at the same address
– Requires a self join of the customers table on address
field
Bookstore SQL302 Module 2 34

35. Theta join results
• Can be further processed with a union query to
consolidate names into a single list
Bookstore SQL302 Module 2 35

36. SQL302
SQL Programming
Part 3– Set Operations
Bookstore SQL302 Module 2 36

37. Set Operations
• More on unions
• Intersect
• Except
Bookstore SQL302 Module 2 37

38. Unions
• Combines two or more tables
• Tables must be union compatible
Bookstore SQL302 Module 2 38

39. Unions
Select <column-list> from
<table1>
Union [ALL]
Select <same-columns> from
<table2>
Bookstore SQL302 Module 2 39

40. Unions
• Example: consolidate two columns into one
column
Bookstore SQL302 Module 2 40

41. Union consolidation result
• Customers in same city
Bookstore SQL302 Module 2 41

42. Unions
• Example: add a total row to a query result
• Code:
use bookstore;
select order_numb
, sum(quantity) as "Quantity"
, sum(cost_line)as "Total Cost"
from orderlines
group by order_numb
union
select NULL, sum(quantity),
sum(cost_line)
from orderlines;
Bookstore SQL302 Module 2 42

43. unions
• Example: add an element to a pick list
Bookstore SQL302 Module 2 43

44. intersect
• The intersect operator finds rows in
common between two tables
• Syntax
Select <column-list> from <table1>
intersect
Select <same-columns> from <table2>
Bookstore SQL302 Module 2 44

45. intersect
• Example: find cities in common between
sources and customers
• Code
select customer_city, customer_state,
customer_zip
from customers
intersect
select source_city, source_state,
source_zip
from sources; SQL302 Module 2
Bookstore 45

46. Except
• Finds all rows from first table that are not
found in the second table
• Syntax:
Select <column-list> from <table1>
except
Select <same-columns> from <table2>
Bookstore SQL302 Module 2 46

47. except
• Example: find sources that are not located
in any of our customer’s cities
• Code
select source_city, source_state,
source_zip
from sources
except
select customer_city, customer_state,
customer_zip
from customers;SQL302 Module 2
Bookstore 47

48. SQL302
SQL Programming
Part 4 – Window Functions
Bookstore SQL302 Module 2 48

49. Aggregate Functions
• Count
• Sum
• Min
• Max
• Avg
• Often used in conjunction with grouping
and window functions
Bookstore SQL302 Module 2 49

50. Window Functions
• Sort of like grouping, but aggregates can
be taken along with straight columns in the
select list
• The function is applied over a window
– Partition by column
– Partition by ()
Bookstore SQL302 Module 2 50

51. Window Functions
Basic syntax:
Select …, window function(column)
partition by <column>
From <table>
where <predicate>
Bookstore SQL302 Module 2 51

52. Window Functions
Example: Show salary along with average for the
job_title and overall
Code:
use employeedb;
select soc_sec_no, name, salary
, SUM(salary) over(partition
by job_title_code) as [Job Code
Average]
, SUM(salary) over() as
[Average]
from employees;
Bookstore SQL302 Module 2 52

53. Exercise
• List all customers and their orders
– Name nicely formatted
– With orders in the year of 1999 (do not use
between, etc.)
– Show total order quantities and amounts
– Only include orders with more than three
order lines
Bookstore SQL302 Module 2 53

54. Notes
Bookstore SQL302 Module 2 54

55. Notes
Bookstore SQL302 Module 2 55