DATATYPES in Objective-C

Creation data matrix barcodes in Objective-C DATATYPES

Interface implemented by all editable and read-only base classes Interface implemented by all editable base classes Interface implemented by all editable collection base classes Interface implemented by all read-only base classes Interface implemented by all read-only collection base classes Interface implemented by CommandBase Clones any serializable object Implements INotifyPropertyChanged

What this chapter covers:

Figure 34-24. Renaming a table The new name is applied throughout the application. If you click the Sales Staff link on the home page, you ll see that the title for the detailed page and the data filter have also been updated. The change is even applied to associated data. Look at the details for the Orders table, and you will see that the column of links to Employee records has also been renamed, as shown in Figure 34-25.

The Oracle database has supported autonomous transactions internally for quite a while. We see them all of the time in the form of recursive SQL. For example, a recursive transaction may be performed when selecting from a sequence, in order for you to increment the sequence immediately in the SYS.SEQ$ table. The update of the SYS.SEQ$ table in support of your sequence is immediately committed and visible to other transactions, but your transaction is not yet committed. Additionally, if you roll back your transaction, the increment to the sequence remains in place; it is not rolled back with your transaction, as it has already been committed. Space management, auditing, and other internal operations are performed in a similar recursive fashion. This feature has now been exposed for all to use. However, I have found that the legitimate realworld use of autonomous transactions is very limited. Time after time, I see them used as a workaround to such problems as a mutating table constraint in a trigger. This almost always leads to data integrity issues, however, since the cause of the mutating table is an attempt to read the table upon which the trigger is firing. Well, by using an autonomous transaction you can query the table, but you are querying the table now without being able to see your changes (which is what the mutating table constraint was trying to do in the first place; the table is in the middle of a modification, so query results would be inconsistent). Any decisions you make based on a query from that trigger would be questionable you are reading old data at that point in time. A potentially valid use for an autonomous transaction is in custom auditing, but I stress the words potentially valid. There are more efficient ways to audit information in the database than via a customwritten trigger. For example, you can use the DBMS_FGA package or just the AUDIT command itself. A question that application developers often pose to me is, How can I log errors in my PL/SQL routines in a manner that will persist, even when my PL/SQL routines" work is rolled back Earlier, we described how PL/SQL statements are atomic they either completely succeed or completely fail. If we logged an error in our PL/SQL routines, by default our logged error information would roll back when Oracle rolled back our statement. Autonomous transactions allow us to change that behavior, to have our error logging information persist even while the rest of the partial work is rolled back. Let s start by setting up a simple error logging table to use; we ll record the timestamp of the error, the error message, and the PL/SQL error stack (for pinpointing where the error emanated from):

The EnterpriseServicesPortal base class handles virtually all the details, allowing a subclass to look like this:

To delete an item, use the DataServiceContext DeleteObject() method with the SaveChanges() method (if you have defined any table constraints or rules you will need to ensure you fulfill them; otherwise this call will fail): static void Main(string[] args) { DataServiceContext ctx = new DataServiceContext(new Uri("http://localhost/9/MovieService.svc")); MovieService.Models.Film FilmToDelete = ctx.Execute<MovieService.Models.Film>(new Uri("Films(1)", UriKind.Relative)).First(); ctx.DeleteObject(FilmToDelete); ctx.SaveChanges(); }

The first letter of the identifier and the first letter of each subsequent concatenated word are capitalized. The first letter of the identifier is lowercase. The first letter of each subsequent concatenated word is capitalized. All letters of the identifier are capitalized. This is used only for identifiers that have two or fewer letters.

Expression Blend. Figure 8-13 shows each element in the Objects and Timeline pane (available on the left side of the window).

Silverlight supports true transparency for all UI Elements. So if you create layer of controls on top of one another and set their Opacity property to varying value, you can see through controls visual. So you can think of using this feature to create a background that shows through the controls that you place on

big_table@ORA11GR2> alter table big_table parallel; Table altered. That is all there is to it parallel query will now be considered for operations against this table. When we rerun the explain plan, this time we see the following: big_table@ORA11GR2> explain plan for 2 select count(status) from big_table; Explained. big_table@ORA11GR2> select * from table(dbms_xplan.display); PLAN_TABLE_OUTPUT ----------------------------------------Plan hash value: 1651916128 ---------------------------------------------------------------------------|Id | Operation | Name |Cost(%CPU)| TQ |IN-OUT|PQ Distrib | ---------------------------------------------------------------------------| 0| SELECT STATEMENT | | 4465 (1)| | | | | 1| SORT AGGREGATE | | | | | | | 2| PX COORDINATOR | | | | | | | 3| PX SEND QC (RANDOM) | :TQ10000 | |Q1,00| P->S |QC (RAND) | | 4| SORT AGGREGATE | | |Q1,00| PCWP | | | 5| PX BLOCK ITERATOR | | 4465 (1)|Q1,00| PCWC | | | 6| TABLE ACCESS FULL| BIG_TABLE| 4465 (1)|Q1,00| PCWP | | ----------------------------------------------------------------------------