- Sams Teach Yourself SQL in 24 Hours, Third Edition
- Table of Contents
- Copyright
- About the Authors
- Acknowledgments
- Tell Us What You Think!
- Introduction
- Part I: A SQL Concepts Overview
- Hour 1. Welcome to the World of SQL
- SQL Definition and History
- SQL Sessions
- Types of SQL Commands
- An Introduction to the Database Used in This Book
- Summary
- Q&A
- Workshop
- Part II: Building Your Database
- Hour 2. Defining Data Structures
- What Is Data?
- Basic Data Types
- Summary
- Q&A
- Workshop
- Hour 3. Managing Database Objects
- What Are Database Objects?
- What Is a Schema?
- A Table: The Primary Storage for Data
- Integrity Constraints
- Summary
- Q&A
- Workshop
- Hour 4. The Normalization Process
- Normalizing a Database
- Summary
- Q&A
- Workshop
- Hour 5. Manipulating Data
- Overview of Data Manipulation
- Populating Tables with New Data
- Updating Existing Data
- Deleting Data from Tables
- Summary
- Q&A
- Workshop
- Hour 6. Managing Database Transactions
- What Is a Transaction?
- What Is Transactional Control?
- Transactional Control and Database Performance
- Summary
- Q&A
- Workshop
- Part III: Getting Effective Results from Queries
- Hour 7. Introduction to the Database Query
- What Is a Query?
- Introduction to the <tt>SELECT</tt> Statement
- Examples of Simple Queries
- Summary
- Q&A
- Workshop
- Hour 8. Using Operators to Categorize Data
- What Is an Operator in SQL?
- Comparison Operators
- Logical Operators
- Conjunctive Operators
- Negating Conditions with the <tt>NOT</tt> Operator
- Arithmetic Operators
- Summary
- Q&A
- Workshop
- Hour 9. Summarizing Data Results from a Query
- What Are Aggregate Functions?
- Summary
- Q&A
- Workshop
- Hour 10. Sorting and Grouping Data
- Why Group Data?
- The <tt>GROUP BY</tt> Clause
- <tt>GROUP BY</tt> Versus <tt>ORDER BY</tt>
- The <tt>HAVING</tt> Clause
- Summary
- Q&A
- Workshop
- Hour 11. Restructuring the Appearance of Data
- The Concepts of ANSI Character Functions
- Various Common Character Functions
- Miscellaneous Character Functions
- Mathematical Functions
- Conversion Functions
- The Concept of Combining Character Functions
- Summary
- Q&A
- Workshop
- Hour 12. Understanding Dates and Times
- How Is a Date Stored?
- Date Functions
- Date Conversions
- Summary
- Q&A
- Workshop
- Part IV: Building Sophisticated Database Queries
- Hour 13. Joining Tables in Queries
- Selecting Data from Multiple Tables
- Types of Joins
- Join Considerations
- Summary
- Q&A
- Workshop
- Hour 14. Using Subqueries to Define Unknown Data
- What Is a Subquery?
- Embedding a Subquery Within a Subquery
- Summary
- Q&A
- Workshop
- Hour 15. Combining Multiple Queries into One
- Single Queries Versus Compound Queries
- Why Would I Ever Want to Use a Compound Query?
- Compound Query Operators
- Using an <tt>ORDER BY</tt> with a Compound Query
- Using <tt>GROUP BY</tt> with a Compound Query
- Retrieving Accurate Data
- Summary
- Workshop
- Q&A
- Part V: SQL Performance Tuning
- Hour 16. Using Indexes to Improve Performance
- What Is an Index?
- How Do Indexes Work?
- The <tt>CREATE INDEX</tt> Command
- Types of Indexes
- When Should Indexes Be Considered?
- When Should Indexes Be Avoided?
- Summary
- Q&A
- Workshop
- Hour 17. Improving Database Performance
- What Is SQL Statement Tuning?
- Database Tuning Versus SQL Tuning
- Formatting Your SQL Statement
- Full Table Scans
- Other Performance Considerations
- Performance Tools
- Summary
- Q&A
- Workshop
- Part VI: Using SQL to Manage Users and Security
- Hour 18. Managing Database Users
- Users Are the Reason
- The Management Process
- Tools Utilized by Database Users
- Summary
- Q&A
- Workshop
- Hour 19. Managing Database Security
- What Is Database Security?
- How Does Security Differ from User Management?
- What Are Privileges?
- Controlling User Access
- Controlling Privileges Through Roles
- Summary
- Q&A
- Workshop
- Part VII: Summarized Data Structures
- Hour 20. Creating and Using Views and Synonyms
- What Is a View?
- Creating Views
- Dropping a View
- What Is a Synonym?
- Summary
- Q&A
- Workshop
- Hour 21. Working with the System Catalog
- What Is the System Catalog?
- How Is the System Catalog Created?
- What Is Contained in the System Catalog?
- Examples of System Catalog Tables by Implementation
- Querying the System Catalog
- Updating System Catalog Objects
- Summary
- Q&A
- Workshop
- Part VIII: Applying SQL Fundamentals in Today's World
- Hour 22. Advanced SQL Topics
- Advanced Topics
- Cursors
- Stored Procedures and Functions
- Triggers
- Dynamic SQL
- Call-Level Interface
- Using SQL to Generate SQL
- Direct Versus Embedded SQL
- Summary
- Q&A
- Workshop
- Hour 23. Extending SQL to the Enterprise, the Internet, and the Intranet
- SQL and the Enterprise
- Accessing a Remote Database
- Accessing a Remote Database Through a Web Interface
- SQL and the Internet
- SQL and the Intranet
- Summary
- Q&A
- Workshop
- Hour 24. Extensions to Standard SQL
- Various Implementations
- Examples of Extensions from Some Implementations
- Interactive SQL Statements
- Summary
- Q&A
- Workshop
- Part IX: Appendixes
- Appendix A. Common SQL Commands
- SQL Statements
- SQL Clauses
- Appendix B. Using MySQL for Exercises
- Windows Installation Instructions
- Linux Installation Instructions
- Appendix C. Answers to Quizzes and Exercises
- Hour 1, "Welcome to the World of SQL"
- Hour 2, "Defining Data Structures"
- Hour 3, "Managing Database Objects"
- Hour 4, "The Normalization Process"
- Hour 5, "Manipulating Data"
- Hour 6, "Managing Database Transactions"
- Hour 7, "Introduction to the Database Query"
- Hour 8, "Using Operators to Categorize Data"
- Hour 9, "Summarizing Data Results from a Query"
- Hour 10, "Sorting and Grouping Data"
- Hour 11, "Restructuring the Appearance of Data"
- Hour 12, "Understanding Dates and Time"
- Hour 13, "Joining Tables in Queries"
- Hour 14, "Using Subqueries to Define Unknown Data"
- Hour 15, "Combining Multiple Queries into One"
- Hour 16, "Using Indexes to Improve Performance"
- Hour 17, "Improving Database Performance"
- Hour 18, "Managing Database Users"
- Hour 19, "Managing Database Security"
- Hour 20, "Creating and Using Views and Synonyms"
- Hour 21, "Working with the System Catalog"
- Hour 22, "Advanced SQL Topics"
- Hour 23, "Extending SQL to the Enterprise, the Internet, and the Intranet"
- Hour 24, "Extensions to Standard SQL"
- Appendix D. <tt>CREATE TABLE</tt> Statements for Book Examples
- <tt>EMPLOYEE_TBL</tt>
- <tt>EMPLOYEE_PAY_TBL</tt>
- <tt>CUSTOMER_TBL</tt>
- <tt>ORDERS_TBL</tt>
- <tt>PRODUCTS_TBL</tt>
- Appendix E. <tt>INSERT</tt> Statements for Data in Book Examples
- <tt>INSERT</tt> Statements
- Appendix F. Glossary
- Appendix G. Bonus Exercises
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What Is the System Catalog?
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The system catalog is a collection of tables and views that contain important information about a database. A system catalog is available for each database. Information in the system catalog defines the structure of the database. For example, the DDL (data dictionary language) for all tables in the database is stored in the system catalog. See Figure 21.1 for an illustration of the system catalog within the database. |
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Figure 21.1 The system catalog.
As you can see in Figure 21.1, the system catalog for a database is actually part of the database. Within the database are objects, such as tables, indexes, and views. The system catalog is basically a group of objects that contain information that defines other objects in the database, the structure of the database itself, and various other significant information.
The system catalog for your implementation may be divided into logical groups of objects to provide tables that are accessible by not only the database administrator, but any other database user as well. For example, a user may need to view the particular database privileges that he or she has been granted, but has no need to know about the internal structure or processes of the database. A user typically queries the system catalog to acquire information on the user's own objects and privileges, whereas the DBA needs to be able to inquire about any structure or event within the database. In some implementations, there are system catalog objects that are accessible only to the database administrator.
The system catalog is crucial to the database administrator or any other database user who needs to know about the database's structure and nature. The system catalog allows order to be kept, not only by the database administrator and users, but by the database server itself.