Oracle 11g: SQL

Module 1Overview of Database Concepts

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Objectives

Define database terms Identify the purpose of a database management

system (DBMS) Explain database design using entity-relationship

models and normalization Explain the purpose of a Structured Query

Language (SQL) Understand how this textbooks topics are

sequenced and how the two sample databases are used

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Database Terminology

Database logical structure to store data

Database management system (DBMS) software used to create and interact with the database

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Database Components

Character Field Record File

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Database Components -Character

Basic unit of data Can be a letter, number, or special symbol

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Database Components - Field

A group of related characters Represents an attribute or characteristic of

an entity

Corresponds to a column in the physical database

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Database Components - Record

A collection of fields for one specific entity Corresponds to a row in the physical

database

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Database Components - File

A group of records about the same type of entity

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Components Example

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Database Example

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Database Management System

Data storage: manage the physical structure of the database

Security: control user access and privileges Multiuser access: manage concurrent data access Backup: enable recovery options for database failures Data access language: provide a language that allows

database access Data integrity: enable constraints or checks on data Data dictionary: maintain information about database

structure

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Database Design

Systems Development Life Cycle (SDLC) Entity-Relationship Model (E-R Model) Normalization

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Systems Development Life Cycle (SDLC)

Systems investigation understanding the problem

Systems analysis understanding the solution

Systems design creating the logical and physical components

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Systems Development Life Cycle (SDLC) (continued)

Systems implementation placing completed system into operation

Systems maintenance and review evaluating the implemented system

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Entity-Relationship Model (E-R Model)

Used to depict the relationship that exists among entities

Model symbols:

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Relationships

The following relationships can be included in an E-R Model: One-to-one

One-to-many

Many-to-many

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E-R Model Notation Examples

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One-to-one Relationship

Each occurrence of data in one entity is represented by only one occurrence of data in the other entity

Example: Each individual has just one Social Security Number (SSN) and each SSN is assigned to just one person

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One-to-many Relationship

Each occurrence of data in one entity can be represented by many occurrences of the data in the other entity

Example: A class has only one instructor, but each instructor can teach many classes

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Many-to-many Relationship

Data can have multiple occurrences in both entities

Example: A student can take many classes and each class is composed of many students

Can not be included in the physical database

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Example E-R Model

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Database Normalization

Determines required tables and columns for each table

Multi-step process Used to reduce or control data redundancy

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Database Normalization (continued)

Data redundancy - Refers to having the same data in different places within a database

Data anomalies - Refers to data inconsistencies

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Unnormalized Data

Contains repeating groups in the Author column in the BOOKS table

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First-Normal Form (1NF)

Primary key is identified Repeating groups are eliminated

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First-Normal Form (1NF) (continued)

ISBN and Author columns together create a composite primary key

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Composite Primary Key

More than one column is required to uniquely identify a row

Can lead to partial dependency - a column is only dependent on a portion of the primary key

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Second-Normal Form (2NF)

Partial dependency must be eliminated Break the composite primary key into

two parts, each part representing a separate table

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Second-Normal Form (2NF) (continued)

BOOKS table in 2NF

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Third-Normal Form (3NF)

Publisher contact name has been removed

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Summary of Normalization Steps

1NF: eliminate repeating groups, identify the primary key

2NF: table is in 1NF and partial dependencies are eliminated

3NF: table is in 2NF and transitive dependencies are eliminated

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Relating Tables within the Database

Once tables are normalized, make certain tables are linked

Tables are linked through a common field A common field is usually a primary key in

one table and a foreign key in the other table

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Structured Query Language (SQL)

Data sublanguage Used to:

Create or modify tables

Add data to tables

Edit data in tables

Retrieve data from tables

ANSI and ISO standards

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Databases used in this Textbook-JustLee Books Database

Assumptions: No back orders or partial shipments

Only US addresses

Shipped orders are purged (deleted) at the end of the month

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Topic Sequence

The first half of the text will focus on creating a database

The second half of the text will focus on querying or retrieving data from a database

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Summary

A DBMS is used to create and maintain a database A database is composed of a group of interrelated

tables

A file is a group of related records; a file is also called a table in the physical database

A record is a group of related fields regarding one specific entity; a record is also called a row

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Summary (continued)

A record is considered unnormalized if it contains repeating groups

A record is in first-normal form (1NF) if no repeating groups exist and it has a primary key

Second-normal form (2NF) is achieved if the record is in 1NF and has no partial dependencies

After a record is in 2NF and all transitive dependencies have been removed, then it is in third-normal form (3NF), which is generally sufficient for most databases

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Summary (continued)

A primary key is used to uniquely identify each record

A common field is used to join data contained in different tables

A foreign key is a common field that exists between two tables but is also a primary key in one of the tables

A Structured Query Language (SQL) is a data sublanguage that navigates the data stored within a databases tables

Module 2Basic SQL SELECT Statements

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Objectives

Distinguish between an RDBMS and an ORDBMS

Identify keywords, mandatory clauses, and optional clauses in a SELECT statement

Select and view all columns of a table Select and view one column of a table Display multiple columns of a table

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Objectives (continued)

Use a column alias to clarify the contents of a particular column

Perform basic arithmetic operations in the SELECT clause

Remove duplicate lists using either the DISTINCT or UNIQUE keyword

Use concatenation to combine fields, literals, and other data

Insert a line break

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Relational Database Management System (RDBMS)

An RDBMS is the software program used to create the database and it allows you to enter, manipulate, and retrieve data

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Object Relational Database Management System (ORDBMS) Same as an RDBMS except it can be used

to reference objects such as maps and object fields

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Create the JustLee Database

Use the provided script to create the database so you can follow the module examples

Verify table contents using the DESCRIBE command

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SELECT Statement Syntax

SELECT statements are used to retrieve data from the database

Syntax gives the basic structure, or rules, for a command

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SELECT Statement Syntax (continued)

Optional clauses and keywords are shown in brackets

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SELECT Statement Syntax (continued)

SELECT and FROM clauses are required SELECT clause identifies column(s) FROM clause identifies table(s) Each clause begins with a keyword

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Selecting All Data in a Table

Substitute an asterisk for the column names in a SELECT clause

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Selecting One Column from a Table

Enter column name in SELECT clause

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Selecting Multiple Columns from a Table

Separate column names with a comma

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Operations Within the SELECT Statement

Column alias can be used for column headings

Perform arithmetic operations Suppress duplicates Concatenate data

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Using Column Aliases

List the alias after the column heading AS keyword is optional Enclose in double quotation marks:

If it contains blank space(s)

If it contains special symbol(s)

To retain case

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Column Alias Example

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Using Arithmetic Operations

Arithmetic operations: Executed left to right

Multiplication and division are solved first

Addition and subtraction are solved last

Override order with parentheses

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Example Arithmetic Operation with Column Alias

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Using DISTINCT and UNIQUE Enter DISTINCT or UNIQUE after SELECT keyword to

suppress duplicates

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Using Concatenation

You can combine data with a string literal Use the concatenation operator, || It allows the use of column aliases

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Concatenation Example

Note: incomplete results shown

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Inserting a Line Break

A line break code of CHR(10) can be used to format output on multiple lines

The output must be formatted as text output in SQL*Plus for the line break command to operate properly

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Summary

Oracle 11g is an ORDBMS A basic query in Oracle 11g SQL includes the SELECT

and FROM clauses, the only mandatory clauses in a SELECT statement

To view all columns in the table, specify an asterisk (*) or list all the column names individually in the SELECT clause

To display a specific column or set of columns, list the column names in the SELECT clause (in the order in which you want them to appear)

When listing column names in the SELECT clause, a comma must separate column names

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Summary (continued)

A column alias can be used to clarify the contents of a particular column; if the alias contains spaces or special symbols, or if you want to display the column with any lowercase letters, you must enclose the column alias in double quotation marks (" ")

Basic arithmetic operations can be performed in the SELECT clause

To remove duplicate listings, include either the DISTINCT or UNIQUE keyword

To specify which table contains the desired columns, you must list the name of the table after the keyword FROM

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Summary (continued)

Use vertical bars (||) to combine, or concatenate, fields, literals, and other data

A line break code of CHR(10) can be used to format output on multiple lines; the output must be formatted as text output in SQL*Plus for the line break command to operate properly

Module 3Restricting Rows and Sorting

Data

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Objectives

Use a WHERE clause to restrict the rows returned by a query

Create a search condition using mathematical comparison operators

Use the BETWEENAND comparison operator to identify records within a range of values

Specify a list of values for a search condition using the IN comparison operator

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Objectives (continued)

Search for patterns using the LIKE comparison operator

Identify the purpose of the % and _ wildcard characters

Join multiple search conditions using the appropriate logical operator

Perform searches for NULL values Specify the order for the presentation of query

results using an ORDER BY clause

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WHERE Clause Syntax

A WHERE clause is used to retrieve rows based on a stated condition

Requires: Column name

Comparison operator

Value or column for comparison

Values are case sensitive

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WHERE Clause Example

List WHERE clause after FROM clause Enclose nonnumeric data in single quotes

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Comparison Operators

Indicate how the data should relate to the given search value

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Arithmetic Comparison Operators

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Other Comparison Operators

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BETWEENAND Operator

Finds values in a specified range

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IN Operator

Returns records that match a value in a specified list

List must be in parentheses Values are separated by commas

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IN Operator Example

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LIKE Operator

Performs pattern searches Used with wildcard characters:

Underscore (_) for exactly one character in the indicated position

Percent sign (%) represents any number of characters

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LIKE Operator Example

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Logical Operators

Used to combine conditions Evaluated in order of NOT, AND, OR:

NOT reverses meaning

AND both conditions must be TRUE

OR at least one condition must be TRUE

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AND Logical Operator Example

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OR Logical Operator Example

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Multiple Logical Operators

Resolved in order of NOT, AND, OR

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Multiple Logical Operators

Use parentheses to override the order of evaluation

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Resolving Multiple Types of Operators

1. Arithmetic operators

2. Comparison operators

3. Logical operators

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Treatment of NULL Values

Absence of data Requires use of IS NULL operator

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Treatment of NULL Values (continued)

A common error is using = NULL which does not raise an Oracle error but it also does not return any rows

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ORDER BY Clause Syntax

The ORDER BY clause presents data in sorted order

Ascending order is default Use DESC keyword to override column

default

255 columns maximum

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ORDER BY Clause Syntax Sort Sequence

In ascending order, values will be listed in the following sequence: Numeric values

Character values

NULL values

In descending order, sequence is reversed

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ORDER BY Example

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ORDER BY Can Reference Column Position

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Summary

The WHERE clause can be included in a SELECT statement to restrict the rows returned by a query to only those meeting a specified condition

When searching a nonnumeric field, the search values must be enclosed in single quotation marks

Comparison operators are used to indicate how the record should relate to the search value

The BETWEEN...AND comparison operator is used to search for records that fall within a certain range of values

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Summary (continued)

The LIKE comparison operator is used with the percent and underscore symbols (% and_) to establish search patterns

Logical operators such as AND and OR can be used to combine several search conditions

When using the AND operator, all conditions must be TRUE for a record to be returned in the results However, with the OR operator, only one condition must be TRUE

A NULL value is the absence of data, not a field with a blank space entered

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Summary (continued)

Use the IS NULL comparison operator to match NULL values; the IS NOT NULL comparison operator finds records that do not contain NULL values in the indicated column

You can sort the results of queries by using an ORDER BY clause; when used, the ORDER BY clause should be listed last in the SELECT statement

By default, records are sorted in ascending order; entering DESC directly after the column name sorts the records in descending order

A column does not have to be listed in the SELECT clause to serve as a basis for sorting

Module 4Joining Data from

Multiple Tables

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Objectives

Identify a Cartesian join Create an equality join using the WHERE clause Create an equality join using the JOIN keyword Create a non-equality join using the WHERE

clause

Create a non-equality join using the JOINON approach

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Objectives (continued)

Create a self-join using the WHERE clause Create a self-join using the JOIN keyword Distinguish an inner join from an outer join Create an outer join using the WHERE clause Create an outer join using the OUTER

keyword Use set operators to combine the results of

multiple queries

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Purpose of Joins

Joins are used to link tables and reconstruct data in a relational database

Joins can be created through: Conditions in a WHERE clause

Use of JOIN keywords in FROM clause

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Cartesian Joins

Created by omitting joining condition in the WHERE clause or through CROSS JOIN keywords in the FROM clause

Results in every possible row combination (m * n)

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Cartesian Join Example:Omitted Condition

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Cartesian Join Example:CROSS JOIN Keywords

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Equality Joins

Link rows through equivalent data that exists in both tables

Created by: Creating equivalency condition in the WHERE

clause

Using NATURAL JOIN, JOINUSING, or JOINON keywords in the FROM clause

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Equality Joins: WHERE Clause Example

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Qualifying Column Names

Columns in both tables must be qualified

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WHERE Clause Supports Join and Other Conditions

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Joining More Than Two Tables

Joining 4 tables requires 3 join conditions

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Equality Joins: NATURAL JOIN

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No Qualifiers with a NATURAL JOIN

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Equality Joins: JOINUSING

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Equality Joins: JOINON

Required if column names are different

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JOIN Keyword Overview

Use JOINUSING when tables have one or more columns in common

Use JOINON when same named columns are not involved or a condition is needed to specify a relationship other than equivalency (next section)

Using the JOIN keyword frees the WHERE clause for exclusive use in restricting rows

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Non-Equality Joins

In WHERE clause, use any comparison operator other than the equal sign

In FROM clause, use JOINON keywords with a non-equivalent condition

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Non-Equality Joins: WHERE Clause Example

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Non-Equality Joins: JOINON Example

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Self-Joins

Used to link a table to itself Requires the use of table aliases Requires the use of a column qualifier

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Customer Table Example

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Self-Joins: WHERE Clause Example

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Self-Joins: JOINON Example

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Outer Joins

Use outer joins to include rows that do not have a match in the other table

In WHERE clause, include outer join operator (+) immediately after the column name of the table with missing rows to add NULL rows

In FROM clause, use FULL, LEFT, or RIGHT with OUTER JOIN keywords

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Outer Joins: WHERE Clause Example

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Outer Joins: OUTER JOIN Keyword Example

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Outer Joins (continued)

If multiple join conditions are used, the outer join condition may be required in all the join conditions to retain non-matching rows

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Set Operators

Used to combine the results of two or more SELECT statements

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Set Operators: UNION Example

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Set Operators: INTERSECT Example

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Set Operators: MINUS Example

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Summary

Data stored in multiple tables regarding a single entity can be linked together through the use of joins

A Cartesian join between two tables returns every possible combination of rows from the tables; the resulting number of rows is always m * n

An equality join is created when the data joining the records from two different tables are an exact match

A non-equality join establishes a relationship based upon anything other than an equal condition

Self-joins are used when a table must be joined to itself to retrieve needed data

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Summary (continued)

Inner joins are categorized as being equality, non-equality, or self-joins

An outer join is created when records need to be included in the results without having corresponding records in the join tables The record is matched with a NULL record so it will be

included in the output

Set operators such as UNION, UNION ALL, INTERSECT, and MINUS can be used to combine the results of multiple queries

Module 5Selected Single-Row Functions

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Objectives

Use the UPPER, LOWER, and INITCAP functions to change the case of field values and character strings

Extract a substring using the SUBSTR function Locate a substring within a character string with the INSTR

function

Nest functions inside other functions Determine the length of a character string using the

LENGTH function Use the LPAD and RPAD functions to pad a string to a

certain width

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Objectives (continued)

Use the LTRIM and RTRIM functions to remove specific characters strings

Substitute character string values with the REPLACE and TRANSLATE functions

Round and truncate numeric data using the ROUND and TRUNC functions

Return the remainder only of a division operation using the MOD function

Calculate the number of months between two dates using the MONTHS_BETWEEN function

Manipulate date data using the ADD_MONTHS, NEXT_DAY, TO_DATE, and ROUND functions

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Objectives (continued)

Extend pattern matching capabilities with regular expressions

Identify and correct problems associated with calculations involving NULL values using the NVL function

Display dates and numbers in a specific format with the TO_CHAR function

Perform condition processing similar to an IF statement with the DECODE function

Use the SOUNDEX function to identify character phonetics Use the DUAL table to test functions

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Terminology

Function predefined block of code that accepts arguments

Single-row function returns one row of results for each record processed

Multiple-row function returns one result per group of data processed (covered in the next module)

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Types of Functions

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Case Conversion Functions

Case conversion functions alter the case of data stored in a column or character string: Used in a SELECT clause they alter the

appearance of the data in the results

Used in a WHERE clause they alter the value for comparison

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LOWER Function

Used to convert characters to lowercase letters

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UPPER Function

Used to convert characters to uppercase letters It can be used in the same way as the LOWER

function: To affect the display of characters it is used in a

SELECT clause To modify the case of characters for a search condition

it is used in a WHERE clause

The syntax for the UPPER function is UPPER(c) Where c is the character string or field to be converted

into uppercase characters

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INITCAP Function

Used to convert characters to mixed case

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Character Manipulation Functions

Character manipulation functions manipulate data by extracting substrings, counting the number of characters, replacing strings, etc.

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SUBSTR Function

Used to return a substring, or portion of a string

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INSTR Function

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Nesting Functions

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LENGTH Function

Used to determine the number of characters in a string

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LPAD and RPAD Functions

Used to pad, or fill in, a character string to a fixed width

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LTRIM and RTRIM Functions

Used to remove a specific string of characters

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REPLACE Function

Substitutes a string with another specified string

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TRANSLATE Function

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CONCAT Function

Used to concatenate two character strings

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Number Functions

Allow for manipulation of numeric data: ROUND

TRUNC

MOD

ABS

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ROUND Function

Used to round numeric columns to a stated precision

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TRUNC Function

Used to truncate a numeric value to a specific position

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MOD Function

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ABS Function

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Date Functions

Used to perform date calculations or format date values Subtract date for number of days difference

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MONTHS_BETWEEN Function

Determines the number of months between two dates

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ADD_MONTHS Function

Adds a specified number of months to a date

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NEXT_DAY Function

Determines the next occurrence of a specified day of the week after a given date

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TO_DATE Function

Converts various date formats to the internal format (DD-MON-YY) used by Oracle 11g

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Format Model Elements - Dates

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ROUND Function

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TRUNC Function

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Regular Expressions

Regular expressions allow the description of complex patterns in textual data

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REGEXP_LIKE

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Other Functions

NVL NVL2 TO_CHAR DECODE SOUNDEX

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NVL Function

Substitutes a value for a NULL value

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NVL2 Function

Allows different actions based on whether a value is NULL

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TO_CHAR Function

Converts dates and numbers to a formatted character string

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Format Model Elements Time and Number

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DECODE Function

Determines action based upon values in a list

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SOUNDEX Function

References phonetic representation of words

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TO_NUMBER Function

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DUAL Table

Dummy table Consists of one column and one row Can be used for table reference in the FROM

clause

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Using DUAL

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Summary

Single-row functions return a result for each row or record processed

Character case conversion functions such as UPPER, LOWER, and INITCAP can be used to alter the case of character strings

Nesting one function within another allows multiple operations to be performed on data

Simple number functions such as ROUND and TRUNC can round or truncate a number on both the left and right side of a decimal

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Summary (continued)

The MOD function is used to return the remainder of a division operation

Date functions can be used to perform calculations with dates or to change the format of dates entered by a user

Regular expressions enable complex pattern matching operations

The NVL and NVL2 functions are used to address problems encountered with NULL values

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Summary (continued)

The TO_CHAR function lets a user present numeric data and dates in a specific format

The DECODE function allows an action to be taken to be determined by a specific value

The SOUNDEX function looks for records based on the phonetic representation of characters

The DUAL table can be helpful when testing functions