Microsoft SQL Server 2008 R2 Unleashed- P80 ppsx

The Attach Databases screen that appears allows you to select the .mdf file and change the file location for any of the related database files.. The steps involved in detaching and attac

Shrinking the Log File

The data file most likely to grow beyond a normal size and require periodic shrinking is

the transaction log file If a user process issues a large update transaction, the log file

grows to the size needed to hold the records generated by the transaction This could be

significantly larger than the normal growth of the transaction log

As with data files, shrinking of the log file in SQL Server 2008 can take place only from

the end of the log file However, you must first back up or truncate the log to remove the

inactive log records and reduce the size of the logical log You can then run the DBCC

SHRINKFILE or DBCC SHRINKDATABASE command to release the unused space in the log file

Transaction log files are divided logically into segments, called virtual log files The

Database Engine chooses the size of the virtual log files dynamically while it is creating or

extending log files Transaction log files can only be shrunk to a virtual log file boundary

It is therefore not possible to shrink a log file to a size smaller than the size of a virtual log

file, even if the space is not being used The size of the virtual log files in a transaction log

increase as the size of the log file increases For example, a database defined with a log file

of 1GB may have virtual log files 128MB in size Therefore, the log can be shrunk to only

about 128MB

Because of the overhead incurred when the autoshrink process attempts to shrink database

files, it is not recommended that you enable this option for the transaction log because it

could be triggered numerous times during the course of a business day It is better to

schedule the shrinking of the log file to be performed during normal daily maintenance,

when production system activity is at a minimum

Using SSMS to Shrink Databases

In addition to shrinking a database by using T-SQL, you can do so through SSMS In the

Object Explorer, you right-click the database you want to shrink, and then you choose

Tasks, followed by Shrink You can then select either Database or Files Selecting the

Database option displays the Shrink Database dialog (see Figure 23.5) The currently

allo-cated size and free space for the database are shown You have the option of selecting the

Shrink Action and checking the Reorganize Files Before Releasing Unused Space check box

You can click the Script button to generate the T-SQL that will be used to perform the

database shrink operation When you do, a DBCC SHRINKDATABASE command is generated

If you want to shrink database files, you choose the Files option instead of Database

Figure 23.6 shows the Shrink File dialog displayed when you select Files You can shrink

one database file at a time using this window If you choose the shrink option Release

Unused Space, SMSS uses the DBCC SHRINKFILE command with the TRUNCATEONLY option

If you choose the Reorganize Pages Before Releasing Unused Space option, SMSS uses the

DBCC SHRINKFILE command without the TRUNCATEONLY or NOTRUNCATE option As

mentioned earlier, this causes page movement to free as much space as possible A

TRUNCATE operation then releases the free space back to the operating system

FIGURE 23.5 Shrinking an entire database using SSMS

FIGURE 23.6 Shrinking database files in SSMS

Moving Databases

Sometimes you need to move a database or database file There are several ways to

accom-plish this task:

Make a database backup and then restore it to a new location

Alter the database, specifying a new location for the database file

Detach the database and then reattach the database, specifying an alternate location

Restoring a Database Backup to a New Location

The database backup option is fairly straightforward You make a backup of the database

and then write it to a file or files The file is restored, and any changes to the location of

the database files are made at that time Backup and restoration are discussed in detail in

Chapter 14

You can easily detach a database by right-clicking the database in the Object Explorer and

choosing Tasks and then Detach When the database is detached, you can move the file(s)

to the desired location You can then right-click on the database’s node and select Attach

The Attach Databases screen that appears allows you to select the mdf file and change the

file location for any of the related database files The steps involved in detaching and

attaching a database are discussed in detail in the later section “Detaching and Attaching

Databases.”

Using ALTER DATABASE

The ALTER DATABASE option for moving user database files was added in SQL Server 2005

This option involves the following steps:

1 Take the database offline

2 Manually move the file(s) to the new location

3 Run the ALTER DATABASE command to set the FILENAME property to the new file

location

4 Bring the database online

The following example uses the ALTER DATABASE command to move the log file for the

AdventureWorks2008 database to the root of the C: drive

ALTER DATABASE AdventureWorks2008

MODIFY FILE (NAME = AdventureWorks2008_Log,

FILENAME = ‘C:\AdventureWorks2008_log.ldf’)

CAUTION

Use caution when specifying the FILENAME parameter to move a database log file If

the FILENAME setting specified in the ALTER DATABASE command is incorrect and the

file does not exist, the command still completes successfully When the database is

brought back online, a message stating that the file can’t be found appears, and a new

log file is created for you This invalidates the old log file

Detaching and Attaching Databases

A convenient way to move or copy database files is to detach and attach databases

Detaching database files removes the database from an instance of SQL Server but leaves

the database files intact After the database is detached, the files associated with the

data-base (that is, mdf, ndf, and ldf files) can be copied or moved to an alternate location

You can then reattach the relocated files by using the CREATE DATABASE command with

the FOR ATTACH option

TIP

The process of detaching and attaching a database is extremely fast It is therefore a

good alternative to BACKUP and RESTORE when you’re copying a database to another

location The catch with detaching a database is that all users must be disconnected

from the database, and the database is unavailable during the detach and copy of the

database files

To detach a database, you right-click the database in Object Explorer and select Tasks and

then Detach Figure 23.7 shows an example of the Detach Database dialog box for

detach-ing the AdventureWorks2008 database You can specify several options, including a handy

option (called Drop Connections) to kill any user processes (SPIDs) that may still be

connected to the database when the detach operation is running If you do not select the

Drop Connections option, and users are still connected to the database, the detach

opera-tion fails

Other options available during the detach operation are also useful The Update Statistics

option updates out-of-date statistics for all the database tables before you detach the

data-base The statistics update can take some time on larger databases, so this slows down the

overall detach operation The other option, Keep Full Text Catalogs, is new to SQL Server

2008 It allows you to detach any full-text catalogs associated with the database These

detached full-text catalogs are then reattached along with the database when the files are

attached See chapter 56 for a more in-depth discussion of full-text catalogs

The attach operation is simple to execute through SMSS In Object Explorer, you simply

right-click the database’s node and select the Attach option The Attach Databases dialog

box appears, allowing you to specify the database file(s) you want to attach You need to

click the Add button to be able to select a database file for restoration When you select

the main mdf file associated with the database, the associated file information for the

other related database files is populated as well

ptg FIGURE 23.7 Detaching a database by using SSMS

23.8 shows the Attach Databases dialog box for the AdventureWorks2008 database The top

portion of the dialog box lists the main (.mdf) database file selected for the

AdventureWorks2008 database The bottom portion lists the related files You have an

option to attach the database with a different name by changing the Attach As name

located at the top of the screen You can also edit the database details at the bottom of

the screen and enter the location of the database files that will be attached The Current

File Path column displays the original file locations determined from the mdf file If the

files were moved to a new location, this is the place to change the current file path to the

new location

You can also accomplish the detach and attach operations by using T-SQL You perform

the detach operation with the sp_detach_db system stored procedure You perform the

attach operation with the CREATE DATABASE command, using the FOR ATTACH option The

following is an example of T-SQL commands for detaching and attaching the

AdventureWorks2008 database:

Detach the database

EXEC master.dbo.sp_detach_db

@dbname = N’AdventureWorks2008’, @keepfulltextindexfile=N’false’

GO

Attach the database

CREATE DATABASE [AdventureWorks2008] ON

( FILENAME = ‘C:\Program Files\Microsoft SQL

FIGURE 23.8 Attaching a database by using SSMS

NOTE

You can use the sp_attach_db procedure to attach a database, but Microsoft

recom-mends that you use the CREATE DATABASE FOR ATTACH command instead The

sp_attach_db procedure has been deprecated and is slated for removal in a future

release of SQL Server

SQL Server 2008 has the capability to attach a database without all the log files You do

this by using the ATTACH_REBUILD_LOG clause when creating the database When you use

this clause, SQL Server rebuilds the log files for you This capability is useful on large

data-bases that may have large logs that are not needed in the environment where the database

files are attached For example, a READ_ONLY database would not need the log files that

may be associated with its production counterpart The following example uses the

ATTACH_REBUILD_LOG clause to create a copy of the AdventureWorks2008 database:

CREATE DATABASE [AdventureWorks2008Temp] ON

( FILENAME = ‘C:\Temp\AdventureWorks2008_Data.mdf’ )

Server\MSSQL.1\MSSQL\Data\AdventureWorks2008_Data.mdf’ ),

( FILENAME = ‘C:\Program Files\Microsoft SQL

Server\MSSQL.1\MSSQL\Data\AdventureWorks2008_log.LDF’ )

FOR ATTACH

FOR ATTACH_REBUILD_LOG

Summary

The steps involved in creating and managing databases are by no means limited to the

topics in this chapter A database consists of many database objects and has a myriad of

other features discussed throughout this book The next chapter, “Creating and Managing

Tables,” delves into one of the most basic elements of a database: the table

Creating and Managing

Tables

What’s New in SQL Server 2008

Creating Tables

Defining Columns

Defining Table Location

Defining Table Constraints

Modifying Tables

Dropping Tables

Using Partitioned Tables

Creating Temporary Tables

Tables are logical constructs used for the storage and

manipulation of data in databases Tables contain columns,

which describe data, and rows, which are instances of table

data Basic relational database design determines the table

and column names as well as the distribution of columns

within tables

This chapter gives you the administrative knowledge you

need to create tables and manage them within your

enter-prise It focuses on the basic constructs for tables and the

table-level features that can make your tables robust and

efficient objects to house your data

What’s New in SQL Server 2008

Most of the new table-oriented features available with SQL

Server 2008 are related to the columns that define a table

Columns can now be defined with several new data types

that further expand the type of data that SQL Server can

store and manage Some of these new types, such as the

FILESTREAM storage and the geometry and geography data

types take SQL Server beyond the typical relational model

FILESTREAM storage provides a reference point to a flat file

in the operating system where the data actually resides, and

the geometry and geography data types bring you into the

world of spatial data storage

The hierarchyid data type is system-provided You use

hierarchyid as a data type to create tables with a

hierarchi-cal structure or to reference the hierarchihierarchi-cal structure of

data in another location You use hierarchyid functions to query and perform work with

hierarchical data by using Transact-SQL (T-SQL)

There have also been additions to more traditional relational data types For example, SQL

Server 2008 now offers separate data types for date and time The new date data type

contains only the date, whereas the new time data type contains only the time portion In

the past, the datetime or smalldatetime data types combined the date and time

compo-nents into a single data type Other date and time data type enhancements are discussed

later in the chapter

SQL Server 2008 also introduces new ways to organize or access columns Sparse columns

and column sets are example of this A sparse column is a column where the majority of

the column’s values contain null values A sparse column is an ordinary column but is

given the SPARSE keyword when it is added to a table so that the SQL Server Database

Engine can optimize the storage of these types of columns The related column set is

another type of column that is XML-typed and identifies all the sparse columns added to

a table These data types and all the new data types are discussed later in this chapter

The good news is that the management of tables and their related columns has remained

relatively unchanged in SQL Server 2008 You will find that the facilities available in the

SQL Server Management Studio are as familiar and as easy to use as they were in SQL

Server 2005

NOTE

This chapter uses examples from Bigpubs2008 database and the Adventureworks2008

database Instructions for installing the BigPubs2008 database are located in the

Introduction chapter at the beginning of this book

Creating Tables

SQL Server 2008 supports the creation of tables using T-SQL, the SQL Server Management

Studio (SSMS) Object Explorer and the SSMS Database Diagram Editor Regardless of the

tool you choose, creating a table involves naming the table, defining the columns, and

assigning properties to the columns The visual tools (such as Object Explorer and

data-base diagrams) are usually the best starting point for creating tables These tools offer

drop-down boxes that allow you to choose the data types for your columns and check

boxes that allow you to define their nullability

This chapter first looks at the visual tools and then delves into the specific parameters

related to the underlying T-SQL statements that ultimately create a table

Using Object Explorer to Create Tables

The Object Explorer in SSMS has a Tables node under each database listed You can add

tables via the Object Explorer by right-clicking this Tables node Figure 24.1 shows the

New Table option displayed after you right-click the Tables node in Object Explorer The

FIGURE 24.1 Using Object Explorer to create a table

top-right side of the screen shown in Figure 24.1 is the table creation screen that allows

you to enter the column name and data type and to set the Allow Nulls option

The data entry area under Column Name is a free-form area where you can define a

column name You can select the data type from the Data Type drop-down, which displays

the data types available with SQL Server The Allow Nulls option is Boolean in nature and is

either checked or not checked For each column selected, a Column Properties section is

displayed in SSMS, providing a myriad of additional properties that you can assign to each

column These properties are discussed in more detail in the “Defining Columns” section,

later in this chapter

Using Database Diagrams to Create Tables

You can use the database diagrams for a more robust visual representation of your tables

You view them from within SSMS, and they give you the distinct advantage of being able

to display multiple tables and the relationships between these tables The Database

Diagram Editor behaves similarly to other data modeling tools that allow you to move

related tables around in the diagram and group them accordingly

Figure 24.2 shows several screens related to database diagrams The left side of Figure 24.2

shows the Object Explorer and the resulting New Database Diagram option that is

displayed if you right-click the Database Diagrams node The right side of the screen

shows the diagram design window In this example, the existing Department table from