Books
in black and white
Main menu
Share a book About us Home
Books
Biology Business Chemistry Computers Culture Economics Fiction Games Guide History Management Mathematical Medicine Mental Fitnes Physics Psychology Scince Sport Technics
Ads

Introduction to the Teradata® RDBMS for UNIX® Version 2 Release 2.1 - NCR

NCR Introduction to the Teradata® RDBMS for UNIX® Version 2 Release 2.1 - NCR, 1998. - 315 p.
Download (direct link): inntroduktionteradata1998.pdf
Previous << 1 .. 33 34 35 36 37 38 < 39 > 40 41 42 43 44 45 .. 76 >> Next


Introduction

Views with Aggregates

Views with Joins

Restrictions on DML Operations on Views

Not every view can be updated (update here means insert, update, and delete), though all views can be queried. Some views cannot be updated for technological reasons, but most that cannot be updated are so restricted by theoretical constraints.

The sets of updatable views are ranked as follows:

• All possible views

• Theoretically updatable views

• A gray area in which views might be theoretically possible, but technology limits the implementation

• Views updatable in SQL

This topic discusses which types of views cannot be updated in the Teradata RDBMS and explains why they cannot be updated.

You cannot update view columns that are aggregates. This means that any column in any view that is defined using any of the following aggregate and logical functions cannot be updated:

• AVG

• SUM

• COUNT

• MAX

• MIN

• DISTINCT

• GROUP BY

• UNION

• JOIN

Views with joins are the classic category of theoretically nonupdatable view. The Teradata RDBMS cannot update a view created with a join.

You can sometimes work around this limitation by using nested subqueries instead of joins.

6-6

Introduction to the Teradata RDBMS for UNIX
Views

For More Information

For More Information

For more information on the topics presented in this chapter, see the following Teradata RDBMS manuals.

IF you want to learn more about . . . THEN see this manual . . .
Views Teradata RDBMS for UNIX Database Design and Administration Teradata RDBMS for UNIX SQL Reference
Teradata SQL Teradata RDBMS for UNIX SQL Reference

Introduction to the Teradata RDBMS for UNIX

6-7
Views

For More Information

6-8

Introduction to the Teradata RDBMS for UNIX
Data Dictionary

Chapter 7

Data Dictionary

Introduction to the Teradata RDBMS for UNIX
Data Dictionary

Introduction to the Teradata RDBMS for UNIX
Data Dictionary

About This Chapter

About This Chapter

The Data Dictionary (DD) is the system catalog for the Teradata Introduction 7 RDBMS. It contains metadata: table and index definitions, view and

macro definitions, resource usage statistics, and much more.

The DD is a system database—a repository containing data about user databases and properties of those databases. The DD also contains a good deal of administrative information about the Teradata RDBMS.

Unlike the system catalogs of nonrelational systems, the Teradata Data Dictionary is a fully relational database that uses SQL as its data sublanguage just like the user databases.

DD Objects

Among the objects defined or administered by the DD are:

• Database and user profiles

• System journals

• Security audit and logon information

• Error and message logs

• Archive information

• Lock journals

• Session status information

• Space allocation information

• Accounting information

• Database, table, view, index, and macro definitions

The DD is useful to all of the following categories of user:

DD Users 7

• System administrator
• Database administrator
• Supervisory users
• Operations control personnel
• End users

This chapter touches briefly on the properties and capabilities of the Data Dictionary (DD).

Introduction to the Teradata RDBMS for UNIX

7-1
Data Dictionary

Structure of the Data Dictionary

Introduction

A Summary of the DD Views

Structure of the Data Dictionary

This topic introduces the components of the DD. In particular, the topic addresses the various supplied views for the DD.

There are roughly 50 different views of DD tables, grouped by user audience in the following table:

User audience Description
End Responsible for personal databases. Needs to know what information is available, what form it is in, how to get it, and what access rights have been granted to others.
Supervisory Responsible for databases and users. Creates and organizes databases, monitors space usage, defines new users, allocates control privileges, creates index, performs archives.
Administrative Responsible for operation and administration of the system. Needs to know about system performance, status and statistics, errors, and accounting.

The following topics list the more important DD views. Note that views with an [x] suffixed to them exist in two forms:

• Without an x, they provide information about the entire group of objects controlled by the view.

• With an x, they provide information only about those objects the user executing the view:

• Owns

• Created

• Has privileges on

7-2

Introduction to the Teradata RDBMS for UNIX
Data Dictionary

Structure of the Data Dictionary

End User Views

Supervisory User Views

The following table lists the more important end user views and their descriptions.

View Description
CharSets Shows the names assigned to user-defined character sets.
Previous << 1 .. 33 34 35 36 37 38 < 39 > 40 41 42 43 44 45 .. 76 >> Next