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Figure 15-3. The Addresses table in the designer mode Note that we designated AddID as a non-null primary key (right-click, select Set Primary Key, and clear the Allow Nulls flag). Also, under the Column Properties you should set the Is Identity property to Yes; this will take care of automatically incrementing the primary key value when inserting new records. Next, create a new database diagram and add/drag your existing two tables, Employees and Addresses, onto it. Before you can add a relationship between these two tables, you must create a new nullable field in the Employees table to store the address foreign key; you should call it AddressID. Now you are ready to link the two tables. First, right-click the Employees table, and select Relationships. Next, click Add to add a new foreign key relationship, name it FK_Employee_Address under Identity, and then click the ellipsis icon next to Tables and Columns Specification under General to configure the relationship. The foreign key table (the table that stores references to rows in another table) is Employees, and this is grayed out since you started by adding a relationship to the Employees table, but you can select the foreign key field to be AddressID. Then select the primary key table to be Addresses, with the field AddID. This will link the two tables by storing unique address IDs in the AddressID field of the Employees table records, giving you a one-to-many relationship between addresses and employees. Figure 15-4 shows our table design canvas after we are done. Similarly, linking two primary keys will yield a one-to-one relationship.

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This trap checks with the configuration file to make sure users have access to the resource. It sets the status code to a security violation if they don t. If this is the case, it terminates the processing of the request with a call to HttpApplication. CompleteRequest. Makes sure the requesting users have NT permissions to access the file. Returns a security exception status and terminates processing of the request if they don t. This module creates the anonymous identification cookie in PostAuthenticate request if it doesn t already exist (and anonymous identification is enabled). This module also uses PostAcquireRequestState to alter the URL when cookieless anonymous identification is being used. The Profile module uses these traps to communicate with the personalization provider to load and store personalization data from persistence. These events were added specifically to implement output caching. This is where, upon entering, the Output Cache module checks incoming requests to see if they match an entry in the cache, and then when it s leaving, it updates the cache with the output if the OutputCache directive directs it to do so.

n this chapter, you ll learn what large objects (LOBs) are and how they re stored in Oracle. You ll also see how to retrieve and manipulate LOBs, and you ll explore some benchmarks comparing various alternatives when manipulating them through the JDBC API.

Note Linking tables via explicit relationships and controlling the nullability of the foreign key columns

Large objects (LOBs) are data types designed to hold large amounts of data. In 9i, a LOB can store up to 4GB of data. In 10g, a LOB can store up to a maximum range of 8TB to 128TB depending on how your database is configured. LOBs are typically used to store unstructured text data, such as text files, and binary data, such as GIFs, multimedia files, Microsoft Word documents, and so on.

gives you fine control of referential integrity. For instance, you will run into a foreign key violation if you try to remove a record that is linked to another by a foreign key constraint. On the other hand, storing raw primary key values without an explicit constraint in related tables will lose these benefits.

The Session module uses these events to retrieve and return state variables from persistence, as selected in configuration. EndRequest is also trapped to be sure the ReleaseRequestState was successfully called (relevant when request processing is terminated programmatically). There is also a Session ID module that is used to manage cookieless session IDs.

Although Oracle supports the LONG data type as well for storing large objects, starting with Oracle 8.0, using LOB data types is strongly recommended for storing large amounts of unstructured data. LOB data types have several advantages over the LONG and LONG RAW types: Larger capacity: LOBs can store up to 4GB of data in 9i and up to a range of 8TB to 128TB of data in 10g depending on your system configuration. LONG and LONG RAW types can store only up to 2GB of data. Restrictions on number of columns: A table can have multiple LOB columns, but it can have only one LONG or LONG RAW column. Random, piecemeal access: LOBs support random access to data, but LONG data types support only sequential access. Object attributes: LOBs can also be object attributes, whereas LONG and LONG RAW cannot.

imperative code, you will sometimes need to use parentheses, as in (...), or begin/end to delimit the regions covered by each branch of the conditional, for example, if x > 100 then (...). If you use the #light syntax option, then these are optional, as long as the branches are correctly indented from the if, elif, and else tokens of the construct.