问题
I have a pFibdataset(which is working similar to BDEDataset) in which I need to make the following join selection
select table.Name as name,
table1.Name as name_1,
table2.Name as name_2
from table
left join table table_1 on table.id=table_1.id
left join table table_2 on table.id=table_2.id
Fields name, name_1 and name_2 are linked to some data-aware edits. Now, I want after I'm modifying(update,delete,insert operations) the name,name_1 and name_2 fields to be updated in the tables. Based on the wiki Using_Multiple_Update_Objects_Index I can use UpdateObjects, or OnUpdateRecord event.
The problem is that I don't understand how this need to be implemented. I have the join select on the query, how I need to define and work with name_1 and name_2 fields. Can someone provide me an example for this?
I know how to use subqueries in order to accomplish this. I need to see how can I can make it by using UpdateObjects or OnUpdateRecord.
回答1:
TpFibUpdateObject works like a trigger on client side. To make it work, set the following properties:
DataSet - dataset (master) to monitor
KindUpdate - Insert/Update/Delete - action to monitor
SQL - command to execute when action is fired, params are taken from DataSet
ExecuteOrder - AfterDefault/BeforeDefault - probably you need after / master
BUT, instead using a lot of UpdateObject components and such tangled approach, I recommend two alternative (read better) ways:
Updatable view. It will work like a "virtual table". Create a view that joins these theee tables and write Before Insert/Update/Delete triggers. In Delphi use it as a regular table: select from view / insert into view / update view and delete from view. Anyway I suppose you need in many places these tables linked toghether.
Use EXECUTE BLOCK statements in your TpFIBDataSet SQLs. Insert / Update / Delete in a batch all tables.
回答2:
Solution : OnUpdateRecord it must be created an TUpdateObject for each field from the joined table.
UpdateObjectvariable.DataSet := Dataset;
fill the SQL text
Apply.
After all update objects are set, UpdateAction := uaApplied; must be called.
来源：https://stackoverflow.com/questions/12366772/delphi-tupdateobject-versus-onupdaterecord-for-a-join-sql-statement