.NET/Java PDF, Tiff, Barcode SDK Library

The module Microsoft.FSharp.Core.Operators includes the definition of a number of useful overloaded math operators. These are shown in Table 3-5 and are overloaded either on a suitable range of integer types or on the basic floating-point types.

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When you have control of the schema of the database, your best option for managing concurrency is to add a timestamp column to the table, and then build a check of the value into the update query. The database automatically updates the timestamp value whenever a change is made to the data. So as long as the timestamp value that was read still matches it when an update is attempted, you can rest assured that the data has not changed in the interim. A timestamp is binary data, so marshaling the value to and from a web browser requires some transformation along the way. You ll send the timestamp value to the browser in a hidden input. When the user sends changes back, you can retrieve it and use it in the where clause of your update. First, you ll need to modify the authors table and add a timestamp column to it. You ll do this on a copy of the authors table named authors_ts, as shown in Figure 10-8.

Well, by now you may have guessed that we need an instead of trigger on the nested table column parts to make the preceding delete work. The trigger code is as follows: benchmark@ORA10G> create or replace trigger parts_io_delete 2 instead of delete on nested table parts of components_or_view 3 begin 4 -- delete from the underlying relational child table 5 delete parts_rel 6 where part_id = :old.part_id; 7 --dbms_output.put_line( sql%rowcount || ' rows deleted'); 8 end; 9 / Trigger created. We are not finished yet. How about if we issue a delete based on the non-nested table columns (i.e., the columns that come from the parent table on which the view is based) benchmark@ORA10G> delete components_or_view 2 where component_id = 1; delete components_or_view * ERROR at line 1: ORA-01732: data manipulation operation not legal on this view For the preceding delete to work, we need a trigger on components_or_view itself. The trigger first deletes the records from the child table parts_rel and then proceeds to delete the parent record in components_rel: benchmark@ORA10G> create or replace trigger components_or_view_io_delete 2 instead of delete on components_or_view 3 begin 4 -- First delete from the child table 5 delete parts_rel 6 where part_id in 7 ( 8 select part_id 9 from TABLE( cast( :old.parts as part_type_tab ) ) 10 ); 11 12 -- then delete from the parent table 13 delete components_rel 14 where component_id = :old.component_id; 15 end; 16 / Trigger created.

abs cos, sin, tan cosh, sinh, tanh acos, asin, atan, atan2 ceil, floor truncate exp, log, log10 ( ** )

Now the same delete should work as follows: benchmark@ORA10G> delete components_or_view 2 where component_id = 1; 1 row deleted. Phew! That completes our section on instead of triggers to enable DMLs on object views. They are complicated (especially the ones enabling updates); however, the fact that they need to be written only once per object view is a bit encouraging from the maintainability point of view. Once the triggers have been written, the calling code can work transparently on them. Of course, you still need to maintain them as the schema changes, but schema changes are relatively rare, in general. In the next section, we will compare the performance of DML statements on solutions that use object views, relational tables, and nested tables to store parent child data.

Figure 10-8. The modified version of the authors table Here s the markup from the editing page. The user will pick an author for editing with the DropDownList. You re only creating an interface to edit the first and last name. Of course, usually you would create an interface for editing more of the data. What you re interested in for this demonstration, though, is the user control created just after the HTML table (see Concurrency3.aspx in Web10). <asp:Panel Runat=server ID=pnEdit Visible=false> <table> <tr> <td>First Name</td> <td> <asp:TextBox Runat=server ID=txtFirstName /> </td> </tr>

Absolute value of signed numeric types Trigonometric functions Hyperbolic trigonometric functions Inverse trigonometric functions Round up, round down Round toward zero Exponent, logarithm, base-10 logarithm Power