1 Chapter 4 Documenting Information Systems Yong Choi BPA CSUB.
Introduction to SQL Yong Choi School of Business CSU, Bakersfield.
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Transcript of Introduction to SQL Yong Choi School of Business CSU, Bakersfield.
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Study Objectives
• Understand the basic commands and functions of SQL
• Learn how SQL is used for data manipulation (to add, modify, delete, and retrieve data)
• Learn how to use SQL to query a database to extract useful information
• Learn how SQL is used for data administration (to create tables, indexes, and views)
• Practice SQL
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Ideal Database Language Requirements
• Create database and table structures. – SQL has a data definition component that gives us the
ability to meet this requirement.
• Manage the data component of the database.– SQL gives us a set of commands to add, update, and
delete data within the database tables.
• Provide detailed data query capability.– "Standard" SQL uses a set of approximately thirty
commands that allow us to retrieve data and to convert the raw data into useful information.
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Introduction to SQL
• Standard Query Language (SQL) is the relational model’s standard language.
• The original version of SQL was developed at IBM's San Jose Research Laboratory. This language, originally called Sequel. The Sequel language has evolved since then, and its name has changed to SQL (Structured Query Language).
• In 1986, the American National Standards Institute (ANSI) published an SQL standard.– In 1992, work was completed on a significantly
revised version of the SQL standard (SQL-92).
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Introduction to SQL (con’t)
• SQL is relatively easy to learn– SQL commands set has a basic vocabulary of less than
100 words.
• SQL is a nonprocedural language. So, it is much easier to use. – Its user merely commands what is to be done without
having to worry about how it's to be done.– Procedural language: COBOL, C, or Pascal.
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Basic Structure of SQL Queries
• SELECT <attribute list>• FROM <table list>• WHERE <condition>• GROUP BY < grouping attribute(s)>• HAVING <group condition>• ORDER BY <attribute list>
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The SELECT and FROM Statement
• The SELECT statement is used to select data from a table. The tabular result is stored in a result table (called the result set). The FROM statement is used to select tables.
• Syntax:– SELECT column_name(s) – FROM table_name
• To select all columns from a table, use a * symbol instead of column names: – SELECT * FROM table_name
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The WHERE Statement
• To conditionally select data from a table, a WHERE clause can be added to the SELECT statement.
• Syntax:– SELECT column – FROM table – WHERE column operator value
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Typical Data Types
• INTEGER: Numbers without a decimal point• SMALLINT: Uses less space than INTEGER• DECIMAL(p,q): P number of digits; q number of
decimal places• CHAR(n): Character string n places long• DATE: Dates in DD-MON-YYYY or MM/DD/YYYY
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Semicolon after SQL Statements?
• Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server.
• MS Access and SQL Server do not require to put a semicolon after each SQL statement, but other database SQLs force you to use it such as Oracle. So, you must use a semicolon for this class.– Access SQL commands are not case sensitive (including
table and attribute names) but try to follow exact names for better readability.
– Download SQL data file form the class web site.
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CustomerNum CustomerName Street City State Zip Balance CreditLimit RepNum
148 Al's Appliance and Sport
2837 Greenway
Fillmore FL 33336 $6,550 $7,500 20
OrderNum PartNum NumOrdered QuotedPrice
21608 AT94 11 $21.95
OrderNum OrderDate CustomerNum
21608 10/20/2003 148
Customer
OrderLine
Order
PartNum Description OnHand Class Warehouse Price
AT94 Iron 50 HW 3 $24.95
Part
RepRepNum LastName FirstName Street City State Zip Commission Rate
20 Kaiser Valerie 624 Randall Grove FL 33321 $20,542.50 0.05
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SQL Example – WHERE clause
• Example 3: Save as example 3– List the name of every customers with
$10,000 credit limit.• Credit limit must be equal to $10000
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SQL Comparison Operators For WHERE clause
NOT Warehouse =‘3’
LIKE: LIKE ‘a*’, LIKE ‘*s’, Like ‘*Oxford*’
(NOT) BETWEEN 45000 AND 78000
(NOT) IN (123, 345)
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SQL Examples
• Example 5: Save as example 5– Find the customer name for every
customer located in the city of Grove
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SQL Examples
• Example 6: Save as example 6– List the number, name, credit limit,
and balance for customers with credit limits that exceed their balances.
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SQL Examples – Compound Conditions
• Example 7: Save as example 7– List the description of all parts that
are located in warehouse 3 and for which there are more than 20 units on hand.
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SQL Examples – Compound Conditions
• Example 8: Save as example 8– List the descriptions of all parts that
are located in warehouse 3 or for which there are more than 20 units on hand.
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SQL Examples
• Example 9: Save as example 9– List the description of all parts that
are not in warehouse 3. – Use “NOT” (i.e., where NOT A = 100;)
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SQL Examples
• Example 10: Save as example 10– List the number, name, and balance
of all customers with balances greater than or equal to $1,000 and less than or equal to $5,000.
– (NOT) BETWEEN 45000 AND 78000
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SQL Examples – Computed Field
• Computed field can involve:– addition(+), subtraction(-), Multiplication(*), or
division (/)
• Example 11: Save as example 11– List the number, name and available
credit for all customers. – Use “AS” for assigning a new field
name
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SQL Examples – Computed Field
• Computed field can involve:– addition(+), subtraction(-), Multiplication(*), or
division (/)
• Example 12: Save as example 12– List the number, name, and available
credit for all customers with credit limits that exceed their balances.
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SQL Examples – LIKE and IN
• Example 13: Save as example 13– List the number, name, and complete
address of every customer located on a street that contain the letters “Oxford.” • Customer names begin with B: Like B*• Customer names end with E: Like *E• Fine exact customer last name: like
‘*Choi*’
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SQL Examples – LIKE and IN
• Example 14: Save as example 14– List the number, name, and credit
limit for every customer with a credit of $7,500, $10,000, or $15,000.
– IN (7500, 10000, 15000);
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SQL Examples
• Default value of ORDER BY: ascending• Example 15: Save as example 15
– List the number, name, and credit limit of all customers. Sort the customers by name in ascending order .
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SQL Examples
• Default value of ORDER BY: ascending• Example 16: Save as example 16
– List the number, name, and credit limit of all customers. Sort the customers by name (minor) in ascending order within credit limit (major) in descending order.
– What about this case? • customer name (minor) and credit limit (major)