.NET/Java PDF, Tiff, Barcode SDK Library

Description ID Length of clob ------------------------------ ---------- -------------Insert from SQL 1 4000 In PL/SQL, the maximum size for the VARCHAR2 variable is 32,760 bytes, so you can insert a string of length up to 32,760 bytes if you use PL/SQL as follows: benchmark@ORA10G> declare 2 l_big_string varchar2(32760) := rpad( '*',32760, '*' ); 3 begin 4 insert into clob_table(x, id, clob_col) 5 values ('Insert from PL/SQL', 2, l_big_string ); 6 end; 7 / PL/SQL procedure successfully completed. benchmark@ORA10G> commit; Commit complete. benchmark@ORA10G> select x "Description", id, 2 dbms_lob.getlength( clob_col ) "Length of clob" 3 from clob_table; Description ID Length of clob ------------------------------ ---------- -------------Insert from SQL 1 4000 Insert from PL/SQL 2 32760 We will soon cover how to insert values bigger than 32,760 bytes in PL/SQL. Let s now clean up and repopulate our clob_table data with a simple row. benchmark@ORA10G> delete from clob_table; 0 rows deleted. benchmark@ORA10G> insert into clob_table (clob_col) 2 values ( 'A clob example' ); 1 row created. In PL/SQL, assigning a VARCHAR2 variable to a CLOB variable creates a temporary CLOB silently. The temporary variable is automatically freed at the end of the block. To find out the information about how many temporary LOBs exist, we can query the view V$TEMPORARY_LOBS. We do that in the procedure print_temporary_lob_info, which is defined as follows: benchmark@ORA10G> create or replace procedure print_temporary_lob_info( p_msg in varchar2 default ' ' ) 2 is

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One of the classes (with the same name as your database) generated by SqlMetal represents the entire database. This class inherits from the DataContext class and carries with it all the connection

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Figure 2-5. Output of the Default.aspx page in an application with our custom global.asax One final note about inheriting from HttpApplication: Using the strategies outlined here, the actual global.asax is nothing more than an Application directive. In Visual Studio .NET 2003, the IDE won t actually show the contents of this file; it has to be opened from the file system with another editor to see the directive. Now in Visual Studio .NET 2005, it won t give you a code-behind. Fickle. Figure 2-6 displays your options when you add a new Global Application Class.

begin dbms_output.put_line ( p_msg ); for i in ( select cache_lobs, nocache_lobs from v$temporary_lobs ) loop dbms_output.put_line( 'cache lobs: ' || i.cache_lobs ); dbms_output.put_line( 'nocache lobs: ' || i.nocache_lobs ); end loop; end; /

details that are used when accessing the data contained in the database through the mapped objects. You can supply a connection string when you instantiate this main database object, as the following code snippet shows (to run this, you will need the Northwnd.mdf file in your source directory): #light #I @"c:\Program Files\Reference Assemblies\Microsoft\Framework\v3.5" #r "System.Core.dll" #r "System.Data.Linq.dll" #r "FSharp.Linq.dll" #r "Northwind.dll" open System open System.Data.SqlClient open Nwind let db = let connB = new SqlConnectionStringBuilder() connB.AttachDBFilename <- __YOUR_SOURCE_DIRECTORY__ + @"\Northwnd.mdf" connB.IntegratedSecurity <- true connB.Enlist <- false connB.DataSource <- @".\SQLExpress" new Northwind(connB.ConnectionString)

Figure 2-6. The Visual Studio .NET 2005 dialog for adding a Global Application Class. Notice the option to Place code in separate file is disabled.

Procedure created. The procedure takes a message string, prints it out, and then loops through the records in the view V$TEMPORARY_LOBS, printing out the columns cache_lobs (number of cached temporary lobs) and nocache_lobs (the number of temporary lobs that are not cached). The following PL/SQL block creates a VARCHAR2 and assigns it to a CLOB variable. Right after that, it invokes the print_temporary_lob_info() method. It then invokes the same method once again after the PL/SQL block ends: benchmark@ORA10G> declare 2 varchar2_data varchar2(100) := 'value in varchar2'; 3 l_clob clob; 4 begin 5 l_clob := varchar2_data; 6 print_temporary_lob_info ( 'after assignment' ); 7 end; 8 / after assignment cache lobs: 1 nocache lobs: 0 PL/SQL procedure successfully completed. benchmark@ORA10G> exec print_temporary_lob_info ( 'after PL/SQL block' ); after PL/SQL block cache lobs: 0 nocache lobs: 0 PL/SQL procedure successfully completed. As highlighted in the preceding code, a temporary LOB was created right after the assignment (note that the LOBs created thus are cached by default). There were no temporary LOBs after the PL/SQL block, as shown by the second execution of print_temporary_lob_info. Let s now look at how to update LOBs in PL/SQL. Regardless of whether you use PL/SQL or Java, for updating a LOB an important thing to remember is that you need to lock the row containing the LOB data before updating it. Note that if you have just inserted the row that you need to update in the same session, then you don t need to explicitly lock it Oracle already has a lock on the inserted row. The reason a lock is required in the first place is

Using LinqToSql from F#