SQL201S Accelerated Introduction to MySQL Queries

Bookstore SQL201S 1
An accelerated introduction to SQL for non-
programmers
P.O. Box 6142
Laguna Niguel, CA 92607
949-489-1472
http://www.ocdatabases.com
Welcome to SQL201S –
Accelerated Introduction to
SQL Queries Using MySQL

Bookstore SQL201S 2
SQL
• Introduction (s)
• Facilities
• Course Packet (contents may vary)
– Student questionnaire (may be onleine)
– Collaterals (Maps, Catalogs, Etc.)
– PowerPoint handouts for all sessions
– Evaluation form (may be online)
– Training certificate

Bookstore SQL201S 3
SQL Curriculum
SQL200*
SQL200S*
SQL212
Oracle
SQL202
Transact-SQL
SQL201W
MySQL
* = included in
above courses

Bookstore SQL201S 4
Accelerated Introduction to SQL
• Assumes no prior knowledge of SQL
• Quick pace for experienced computer users
• End-user, not programmer, oriented
• Focus is on SQL, not Workbench
• SQL201S is first two modules of SQL201,
otherwise identical.

Bookstore SQL201S 5
SQL
• Select
– Basic
– Filters
– Special Operators
– Multi-table retrieval
• Joins
• Subqueries
• Unions
– Calculations and
Aggregates
SQL CoveredSQL Covered::

Bookstore SQL201S 6
SQL
• 2 Sessions
• Lecture
• Demo
• Student “hands-on”
• Many exercises are cumulative –
later examples build on queries
created earlier
Course Format:Course Format:

Bookstore SQL201S 7
SQL
• Session 1 – Basic SQL
• Session 2 – Multi-table
Retrieval
Course Schedule (“1/2” day sessions):Course Schedule (“1/2” day sessions):

Bookstore SQL201 Module 1 9
SQL201
MySQL Programming
Based on SQL Clearly Explained by Jan Harrington
Module 1 – Relational Database Background,
Basic Single Table Retrieval Operations

Note on SQL201 Slides
• These slides were originally designed to support the
single SQL200 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 slides out into
their own slide sets.

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

SQL201 Contact Information
P.O. Box 6142
949-489-1472
http://www.d2associates.com
slides.1@dhdursoassociates.com
Copyright 2001-2015. All rights reserved.

SQL201 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?
support@ocdatabases.com

SQL Programming
• Course focus is SQL language
• Widely used for:
– Database administration
– Enterprise application development
– Data driven web sites
• A foundation skill for eBusiness and
almost all major business applications that
use relational databases

SQL Programming
• A basic knowledge of query systems,
perhaps via MS Access, or some
programming knowledge, is desirable
• We will use GUI tools such as MySQL
workbench in this class. But we will be
typing up the scripts directly in SQL code.

Relational Database Evolution
• Based on Codd’s paper
• Early commercial efforts focused on Unix
• First mainframe implementation by IBM -
precursor to today’s DB2
• First PC implementation in early 80’s by
Oracle

Relational Database Basics
• Storage
• Databases
• Tables
• Rows
• Columns
• Indexes
• Views
• Cursors
• Application interfaces

Relational Database Table

Constraints
• Database
– Domain
– Uniqueness
– Relationship
Cardinality
• 1 to 1
• 1 to N
• Other Business Rule
– Triggers
– Stored Procedures

Relational Database with constraints

Database Management Systems
Positioning Chart
VLDB
Enterprise
Workgroup
Single user
Spreadsheet
# Users
Cost

System Architecture
Access
MDB
File Server
Architecture
Access

System Architecture
Oracle
DB
Visual
Basic App
Client/Server
Architecture
Access
SQL

System Architecture
Oracle
DB
Browser
Web
Architecture
Web
Server
SQL

Approaching SQL
• Relatively simple
• Two main environments
– Interactive (This course)
– Embedded
• Static (Compiled)
• Dynamic

SQL Standardization
ANSI standardization
– First standard in 1986
– SQL 89
– SQL 92
– SQL 99
• Various vendor extensions
– Microsoft/Sybase: T-SQL
– Oracle: PL/SQL

SQL Conformance
• Entry
• Intermediate
• Advanced
• Most are at least entry level

SQL Statements
• Data Manipulation Language (DML)
• Data Control Language (DCL)
• Data Definition Language (DDL)
• Note: SQL 99 changes these to seven types

SQL DDL
• Data definition language (DDL)
– Create, alter, drop, etc.
– Frequently implemented via various CASE
tools: Visio, Embarcadero, ERWin, etc.
– But very useful for database administration

SQL DCL
• Data Control Language (DDL)
– Grant
– Revoke
– Deny
– Constraints

SQL DML
• Data Manipulation Language (DML)
– Select
– Insert
– Update
– Delete

SQL Statement Processing
Parse
Validate
Optimize
Access Plan
Execute

Bookstore Sample Database
• Before we continue (note: instructor may have
already done this)…
• Load the sample database if you haven’t already
– Run the supplied SQL script

Text Conventions
• In an enterprise database such as Oracle or
MySQL enclose text strings in single
quotes
– ‘Jones’

Date Conventions
• In an enterprise database enclose dates in
single quotes
– ‘2004-12-23’ MySQL
– ’12-23-2004’ SQL Server
– ’23-DEC-04’ Oracle

Select statement clauses
SELECT columns
FROM tables
WHERE condition
GROUP BY columns
HAVING condition
ORDER BY columns

SELECT
Basic Syntax (Projection):
Select <column-list> or <*>
From <table-list>

SELECT
Basic Example (Projection):
select
customer_last_name,
customer_street
from customers

MySQL Query

SELECT with Where Clause
Example (Restriction plus Projection):
Select <column-list> or *
From <table-list>
Where <selection-criteria>;

Comparison Operators
• < less than
• > greater than
• <= less than or equal to
• >= greater than or equal to
• = equal to
• <> or != two forms for not equal

SELECT with Where
Basic Example (Restriction plus Projection):
select customer_last_name,
customer_first_name,
customer_street
from customers
where customer_last_name =
‘Jones’

Select with Where

On Your Own
• Find books written by Mark Twain
• Show title, publisher, year

Complex Predicates
Follow normal boolean logic
Select customer_last_name,
customer_first_name,
customer_street, customer_state
From customers
Where (customer_last_name = ‘Jones’ or
customer_last_name = ‘Smith’)and
customer_state=‘NY’

Select with Complex Where

Complex Where Result

Special Operators
• Can be used in where clause
• LIKE
• IN
• BETWEEN
• IS NULL
• EXISTS

Like (“Wild Card Matches”)
• Use ANSI wildcard
characters: % _
• Where
customer_last_name
like ‘Jo%’
like ‘Jo_’
There are also additional regular
expression search patterns

IN
Select *
From customers
Where customer_last_name in
(‘Rizzo’, ‘Jones’, ‘Garcia’);
The list in parentheses can be replaced by a
subquery. We will study this later.

SQL Where Clause with IN

IS NULL
SQL uses three valued logic. A null is NOT the
same as blank or empty. It means missing or
unknown.

IS NULL
Select *
From customers
Where customer_street IS
NULL;
Must use IS NULL to test for NULL values.
Cannot even use = NULL.

On Your Own
• Find all customers with an address not equal to
4592 Maple Lane
• Was Peter Johnson selected?
• Why or why not?

BETWEEN
List all orders placed in 1999.
select *
from orders
where order_date BETWEEN
‘1999-01-01’ and ‘1999-12-
31’;
Note: date formats vary from product to product; recent
versions tend to be pretty flexible.

Where with Between

Removing Duplicates
Select DISTINCT
customer_city
From customers;
List once each city in which there are
customers
Removes duplicate rows from result set

Removing Duplicates

Sorting – ORDER BY
DESC will sort in descending order
Basic syntax:
Select <column list> or *
From <table list>
Where <selection criteria>
Order by <column list> [DESC]

Sorting – ORDER BY
select *
from orderlines
order by cost_line desc,
isbn;
List all orderlines sorted by cost
descending

Sorting Results with Order By

Limiting Record Selection
Select order_numb, isbn,
cost_line
From orderlines
Order by cost_line desc, isbn
limit 5;
List largest 5 orderlines…

Select…limit 5

SQL Exercises
• List all books whose publisher name begins
with “H” or “T”; sort by title [hint: use LIKE]
• List all customers whose last name ends with
“S”; sort by state, city, last name
• Find the order numbers of orders with order
dates in 1999; sort by order #. [Hint: use
BETWEEN]
• Find the order numbers and order dates of all
orders with a “2” in character position 2 of the
credit card #; sort by order date descending
[end module]

Notes

SQL201
SQL Programming
Workshop 2 – Joins, Subqueries, Unions,
Calculations and Grouping
Based on SQL Clearly Explained by Jan Harrington

Note on SQL201 Slides
• These slides were originally designed to support the
single SQL201 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 slides out into their
own slide sets.

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

SQL201 Contact Information
P.O. Box 6142
949-489-1472
http://www.d2associates.com
slides.1@dhdursoassociates.com
Copyright 2018 All rights reserved.

SQL201 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?
support@ocdatabases.com

SQL201
SQL Programming
Part 1 – Joins

Relational Database with constraints (from text)

Joins
• Inner
• Outer
– Left
– Right
– Full
• Cross
• Self
• Theta
• We will cover the most important; others as time
and interest permit

Inner Join
• Pairs each row from first table
with corresponding row from
second table over the “join
column”
• The result set only contains
rows where there is a match
over the join column in both
tables
• Equi-join is the common inner
join

Inner Join
Older Syntax:
Select <column-list>
From <tablelist>
Where <predicate>
Still very commonly used

Inner Join
Example using older syntax:
SELECT customer_first_name,
customer_street, order_numb,
order_date
from customers, orders
Where customers.customer_numb =
orders.customer_numb

Inner Join with Result

Inner Join (New Syntax)
Basic SQL 92 Syntax:
From <table1>
Inner join <table2>
On <join condition>

Inner Join
Basic Example:
order_date
from customers
inner join orders
on customers.customer_numb =
orders.customer_numb

Inner Join with Result

Inner Join over Multiple columns
• Note that that the join condition can apply
to multiple columns if desired
• Used with composite keys

Inner Join
• In the last example…
– What was the cardinality of the relationship
between customers and orders?
– Which table was the parent?
– What was it’s primary key?
– In which table did we employ a foreign key
and what was it?

Cross Join
• What happens when you omit a join
expression?
• Get the cartesian product of the tables – all
possible combinations of the two tables
• For large tables this will run a long time!
• There are uses for these which we will
save for an advanced class

Joining More than Two Tables
• Can join several tables in one select
• Try to limit to three or four
• Join order can be important for
performance (although optimizers will
usually handle this for you)
• Use parentheses to force order of
evaluation (also vendor extensions, often
called “hints”)

Joining More than Two Tables
• Add orderlines detail to previous queries
SELECT customer_first_name, customer_street,
orders.order_numb, orders.order_date,
orderlines.isbn, orderlines.quantity
FROM customers
INNER JOIN orders ON
customers.customer_numb=orders.customer_numb
INNER JOIN orderlines
on orders.order_numb = orderlines.order_numb

Correlation Names (Table Aliases)
Basic Example:
order_date
from customers as c
inner join orders as o
on c.customer_numb = o.customer_numb
alias

Multi-table Join with Results

On Your Own
• Add the book title to the previous query
results
• Hint: add another join to books table
Bookstore 92SQL201 Module 2

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

Left Outer Join
Basic SQL 92 Syntax:
From <table1>
Left [outer] join
<table2>
On <join condition>

Left-Join
Basic Example:
order_date
from customers as c
left join orders as o
on c.customer_numb =
o.customer_numb

Left Join with Results

Negative query
• Add where clause to outer join
• Restrict to nulls on a column from the
child table that cannot be null in the actual
table
– This implies there is no child record
• This is a classic “forensics” query. It finds
unmatched or missing information.

Negative Join Example
• Find customers that have not placed any orders

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

Self Joins
SELECT e.name, m.name as manager
FROM employees AS e
left join employees AS m
on e.mgr_soc_sec_no = m.soc_sec_no;

Self Join Example

SQL201
SQL Programming
Part 2– Subqueries, Unions

Subqueries
• One select statement embedded in another
• Can be nested multiple levels deep
• Can be used in select, from and where
clauses
• Two types:
– Uncorrelated – executes inner query then outer
– Correlated – executes inner query once for
each outer query row

Uncorrelated Subquery
select isbn, quantity
from orderlines
where order_numb in
(select order_numb from
orders where order_date
between ‘1/1/99’ and
‘12/31/99’);

Uncorrelated Subquery with Results

Negative Subquery
• A type of subquery that matches “not
found” conditions

Negative Subquery
select isbn, quantity
from orderlines
where order_numb not in
(select order_numb from
orders where order_date
between ‘1/1/99’ and
‘12/31/99’);

Negative Subquery with Results

Correlated Subquery with Exists
• Inner subquery executed once for each outer row
• Exists will return true or false depending on
whether the result will have any rows or not
• Can be a quick way to test for existence of
records (parent records, say) as used in
application enforcement of referential integrity
This type of query covered in intermediate SQL class

Unions
• Combines two or more tables
• Tables must be union compatible

Unions
Select <column-list> from
<table1>
Union [ALL]
Select <same-columns> from
<table2>

Unions Mailing List Script
select <sources table columns>
from sources
union
select <customers table
columns>
from customers

Unions Mailing List Result

SQL201
SQL Programming
Part 3 – Calculations, Aggregates

Calculated Fields
• Can add a column calculated from others
SELECT order_numb, quantity,
cost_each,
quantity*cost_each as
extension
FROM orderlines

Calculated field in the Result

String Manipulation
• Concatenation
• Trim
• Substring
• Upper, Lower
• Etc. (various vendor extensions)

Concatenation
• Used for concatenated keys
• Useful to format reports
Basic syntax:
(Access) Field1 & Field2
(Oracle, std) Field1 || Field2
(Sql Server) Field1 + Field2

Concatenation
select concat
(rtrim(customer_first_name)
, ‘ ‘ ,
trim(customer_last_name))
as FullName
from customers

Concatenation

Date Functions
• Numerous date functions
• Often vendor specific
• Often used:
– year
– month
– Date_Add(…), DateDiff(…)
– Current_date(), Date_Format
• Ex: where year(order_date) = 1999

Date Format

Aggregate Functions
• Count
• Sum
• Min
• Max
• Avg
• Often used in conjunction with grouping

Aggregate Functions
Basic syntax:
Select <function>(<column>)
From <table>
Group by <column-list>
Having <predicate>
Group by all columns to left of one(s)
you want to aggregate

Aggregate Functions
SELECT order_numb, Count(*) AS
’Number of Order Lines’ ,
Sum(quantity) AS ‘Total Quantity’,
Sum(quantity * cost_each) AS ‘Total
Amount’
FROM order_lines
GROUP BY order_numb
having count(*) > 1;

Aggregate Functions

Having vs. Where
• Having and Where clauses are similar but
not the same
• Having removes groups after they are
formed
• Where removes rows before groups are
formed

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

Exercise Result
[end module]

Notes

SQL201S Accelerated Introduction to MySQL Queries

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