Question

We have an application written in Delphi 2010 which connects to SQL Server Database. Now we’re in the process of migrating to Oracle. With SQL Server it was very easy to perform insert, update, delete right from a dbgrid connected to a Stored Procedure.

It’s because stored procedures in SQL Server can easily act as a table so that you can do any operation on it, providing it returns the necessary columns within the resultset. Now with Oracle I don’t know how do do it. I connect a DBGrid to a DataSource, dataset of which is a Stored Procedure object,but I can’t edit the grid. Just Select is possible.

What do I have to do to to achieve this?I use UniDac component suite to connect to Oracle database.

Answer 1

OK,here I’m answering the question though I can see very few are dealing with Delphi recently. Let’s say we have a stored proc in Oracle database:

CREATE OR REPLACE PROCEDURE GET_EMPLOYEES
 (V_CUR IN OUT SYS_REFCURSOR)
AS
BEGIN
  OPEN V_CUR FOR SELECT * FROM EMPLOYEES;
END GET_EMPLOYEES;

Now, in Delphi you pick a stored procedure component (probably from ODAC or UniDac component suite).Set its StoredProcName GET_EMPLOYEES. Then you can add all the fields that the procedure returns in a cursor.If you run the application and activate the stored procedure you’ll be able to see all the records. But if you try to insert, modify or delete anything you’ll fail to do so. Now, there’s a very tricky thing. If you check, you’ll see that ReadOnly property of all fields are set to True. Even after you set them to False nothing will change in the real database, although you can edit the DBGrid.

So, we’ve come to the main part. How did the old Delphi-SQL Server partnership work so that you could do any operation right from a DBGrid? Well, we must understand that there’s no magic. If it’s SQL, then SQL has only one way of INSERTING,UPDATING and DELETING records-it’s with the appropriate SQL statements.With Delphi-SQL Server there seems to be an implicit SQL statement that we never paid attention. But with Oracle, we have to provide our own statements for each operation.
If you use UniDac or ODAC then there’s SQLInsert,SQLUpdate,SQLDelete properties in a StoredProc object.If you want to insert a record through DBGrid, then you should edit its SQLInsert property to

INSERT INTO EMPLOYEES VALUES(:EMPLOYEEID,:EMPLOYEENAME)

where variables following : are corresponding to te fields of the stored procedure.They’re simply bind variales.When updating and deleting though you’ll need some unique value to represent a specific record. Primary key is one option(maybe the only option as I haven’t been able to figure out how to use ROWID for the same purpose).So the sql statements for UPDATE and DELETE would be

DELETE FROM EMPLOYEES WHERE EMPLOYEEID=:EMPLOYEEID

and

UPDATE EMPLOYEES SET EMPLOYEENAME=:EMPLOYEENAME WHERE EMPLOYEEID=:EMPLOYEEID

P.S. I just found a way to use ROWID for update and delete statements. In your stored procedure if you choose ROWID too and give it an alias then you can construct your UPDATE and DELETE Statements like such:

UPDATE EMPLOYEES SET EMPLOYEENAME=:EMPLOYEENAME,..... WHERE ROWID=:RECORD_ROWID
DELETE FROM EMPLOYEES WHERE ROWID=:RECORD_ROWID

In the preceding statements RECORD_ROWID is the fieldname returned from stored procedure as a result of aliasing ROWID. If you use :ROWID instead you’ll get “ORA-01745: invalid host/bind variable name” error. This is because in a binding variable a colon cannot be followed by a reserved word. And ROWID is a reserved word.