Beginning Microsoft SQL Server 2008 ... - S3 Tech Training
Beginning Microsoft SQL Server 2008 ... - S3 Tech Training Beginning Microsoft SQL Server 2008 ... - S3 Tech Training
Chapter 5: Creating and Altering Tables The ALTER Statement OK, so now we have a database and a couple of nice tables — isn’t life grand? If only things always stayed the same, but they don’t. Sometimes (actually, far more often than we would like), we get requests to change a table rather than re-create it. Likewise, we may need to change the size, file locations, or some other feature of our database. That’s where our ALTER statement comes in. Much like the CREATE statement, our ALTER statement pretty much always starts out the same: ALTER This is totally boring so far, but it won’t stay that way. We’ll see the beginnings of issues with this statement right away, and things will get really interesting (read: convoluted and confusing!) when we deal with this even further in our next chapter (when we deal with constraints). ALTER DATABASE 136 Let’s get right into it by taking a look at changing our database. We’ll actually make a couple of changes just so we can see the effects of different things and how their syntax can vary. Perhaps the biggest trick with the ALTER statement is to remember what you already have. With that in mind, let’s take a look again at what we already have: EXEC sp_helpdb Accounting Notice that I didn’t put the quotation marks in this time as I did when we used this stored proc earlier. That’s because this system procedure, like many of them, accepts a special data type called sysname. As long as what you pass in is a name of a valid object in the system, the quotes are optional for this data type. So, the results should be just like they were when we created the database: Name db_ size Owner dbid Created Status Compatibility_ level Accounting 15.00 MB sa 9 May 28 2000 Status=ONLINE, Updateability=READ_WRITE, UserAccess=MULTI_USER, Recovery=FULL, Version=598, Collation=SQL_Latin1_ General_CP1_CI_AS, SQLSort-Order=52, IsAutoCreateStatistics, IsAutoUpdate- Statistics, IsFullTextEnabled 90
And . . . Name Fileid Filename Filegroup Accounting 1 c:\ Program Files\ Microsoft SQL Server\ MSSQL10 .MSSQLSERVER \MSSQL\DATA \Accounting- Data.mdf AccountingLog 2 c:\ Program Files\ Microsoft SQL Server\ MSSQL10 .MSSQLSERVER \MSSQL\DATA \Accounting- Log.ldf Let’s say you want to change things a bit. For example, let’s say that we know that we are going to be doing a large import into our database. Currently, our database is only 15MB in size — that doesn’t hold much these days. Since we have Autogrow turned on, we could just start our import, and SQL Server would automatically enlarge the database 5MB at a time. Keep in mind, however, that it’s actually a fair amount of work to reallocate the size of the database. If we were inserting 100MB worth of data, then the server would have to deal with that reallocation at least 16 times (at 20MB, 25MB, 30MB, and so on). Since we know that we’re going to be getting up to 100MB of data, why not just do it in one shot? To do this, we would use the ALTER DATABASE command. The general syntax looks like this: Chapter 5: Creating and Altering Tables PRI- MARY Size Maxsize Growth Usage 10240 BK NULL 5120K B 51200KB 5120KB data only 25600KB 5120KB log only ALTER DATABASE ADD FILE ([NAME = ,] FILENAME = [, SIZE = ] [, MAXSIZE = < size in KB, MB, GB or TB >] [, FILEGROWTH = ]) [,...n] [ TO FILEGROUP filegroup_name] [, OFFLINE ] 137
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And . . .<br />
Name Fileid Filename Filegroup<br />
Accounting 1 c:\<br />
Program<br />
Files\<br />
<strong>Microsoft</strong><br />
<strong>SQL</strong> <strong>Server</strong>\<br />
MS<strong>SQL</strong>10<br />
.MS<strong>SQL</strong>SERVER<br />
\MS<strong>SQL</strong>\DATA<br />
\Accounting-<br />
Data.mdf<br />
AccountingLog 2 c:\<br />
Program<br />
Files\<br />
<strong>Microsoft</strong><br />
<strong>SQL</strong> <strong>Server</strong>\<br />
MS<strong>SQL</strong>10<br />
.MS<strong>SQL</strong>SERVER<br />
\MS<strong>SQL</strong>\DATA<br />
\Accounting-<br />
Log.ldf<br />
Let’s say you want to change things a bit. For example, let’s say that we know that we are going to be<br />
doing a large import into our database. Currently, our database is only 15MB in size — that doesn’t hold<br />
much these days. Since we have Autogrow turned on, we could just start our import, and <strong>SQL</strong> <strong>Server</strong><br />
would automatically enlarge the database 5MB at a time. Keep in mind, however, that it’s actually a fair<br />
amount of work to reallocate the size of the database. If we were inserting 100MB worth of data, then the<br />
server would have to deal with that reallocation at least 16 times (at 20MB, 25MB, 30MB, and so on).<br />
Since we know that we’re going to be getting up to 100MB of data, why not just do it in one shot? To do<br />
this, we would use the ALTER DATABASE command.<br />
The general syntax looks like this:<br />
Chapter 5: Creating and Altering Tables<br />
PRI-<br />
MARY<br />
Size Maxsize Growth Usage<br />
10240<br />
BK<br />
NULL 5120K<br />
B<br />
51200KB 5120KB data<br />
only<br />
25600KB 5120KB log<br />
only<br />
ALTER DATABASE <br />
ADD FILE<br />
([NAME = ,]<br />
FILENAME = <br />
[, SIZE = ]<br />
[, MAXSIZE = < size in KB, MB, GB or TB >]<br />
[, FILEGROWTH = ]) [,...n]<br />
[ TO FILEGROUP filegroup_name]<br />
[, OFFLINE ]<br />
137
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