what is the statement for "where" condtion in pl/sql - sql

Question

I want to make a trigger that will be executed for each row before delete on the table Clients, what I'm trying to do is when some one tries to delete a row :
DELETE FROM Clients WHERE id=5 AND name = 'test';
I want to print something on the screen like :
"you deleted with the following conditions : id is 5 , name is test "
or execute another query with same conditions ...
Any kind of help is very appreciated
EDIT
let's suppose the user typed the following query : DELETE FROM Clients where name = 'test'
create or replace
TRIGGER DELETECLIENT
BEFORE DELETE ON CLIENTS
DECLARE
pragma autonomous_transaction;
name1 clients.name%Type;
BEGIN
select name into name1 from clients where name = %I want here the name in the user query %;
IF name1 != null THEN
DELETE FROM clients WHERE name = name1;
commit;
END IF;
END;
what I've tested :
i tried adding :old.name , and :new.name , but this doesn't work when the the row doesn't exist in my database
PS : i'm doing this for educational purpose only, I know the script doesn't make sense. i just wan't to know how to achieve the following task : getting the parameters typed after WHERE in the query

Answer 1

The correlation names and pseudorecords the represent, i.e. :old and :new by default, only have any meaning for row-level triggers:
Note:
This topic applies only to triggers that fire at row level—that is, row-level simple DML triggers and compound DML triggers with row-level timing point sections.
You cannot refer to these in a statement-level trigger, and only :old would have any meaning in a delete trigger. On the other hand, statement-level triggers fire even if no data is affected, whereas a row-level trigger won't fire if, in your example, no data is deleted - because there are no matching rows in your table. (This applies for instead of triggers for views as well, in case you're wondering if that would be a workaround).
So basically you can't do what you're attempting - conditionally deciding whether to delete from another table instead - from a trigger. Triggers are rarely the right answer. For your 'scenario where if it doesn't exist on my table i should try to find it on other site and delete it' you can try to delete a row locally, test whether it did anything, and then decide to delete from the remote table if it didn't. In a PL/SQL block that might be as simple as:
create procedure delete_client(p_name clients.name%type) as
begin
delete from clients where name = p_name;
if sql%rowcount = 0 then
delete from clients#site2 where name = p_name;
end if;
end delete_client;
/
And rather than deleting directly from the table, you make everyone call the procedure instead. Say you start off with some data:
select * from clients;
ID NAME
---------- ----------
1 Joe
2 Anna
select * from clients#site2;
ID NAME
---------- ----------
1 Joe
3 Max
Then calling the procedure for two names:
exec delete_client('Joe');
exec delete_client('Max');
... has removed local and remote records appropriately:
select * from clients;
ID NAME
---------- ----------
2 Anna
select * from clients#site2;
ID NAME
---------- ----------
1 Joe
Joe was only deleted from the local schema despite existing in both; Max didn't exist locally so was deleted from the remote schema.
It doesn't have to be a procedure; if you're deleting through JDBC etc. you can test the result of an execute() call to see how many rows were affected, which is all sql%rowcount is doing really, and the application code can decide whether to do the second delete.
But with a procedure (probably in a package) you can grant execute on that, and remove delete privileges from the users, so they can't bypass this check and do a straight delete from clients where ...
If you really want some 'display' output for testing purposes:
create procedure delete_client(p_name clients.name%type) as
begin
delete from clients where name = p_name;
if sql%rowcount > 0 then
dbms_output.put_line('Deleted ' || sql%rowcount
|| ' rows from local schema for "' || p_name || '"');
else
delete from clients#site2 where name = p_name;
if sql%rowcount > 0 then
dbms_output.put_line('Deleted ' || sql%rowcount
|| ' rows from remote schema for "' || p_name || '"');
else
dbms_output.put_line('No rows deleted on local or remote schema for "'
|| p_name || '"');
end if;
end if;
end delete_client;
/
set serveroutput on
exec delete_client('Joe');
anonymous block completed
Deleted 1 rows from local schema for "Joe"
exec delete_client('Max');
anonymous block completed
Deleted 1 rows from remote schema for "Max"
exec delete_client('Fred');
anonymous block completed
No rows deleted on local or remote schema for "Fred"
But you shouldn't assume anyone calling your procedure will have serveroutput on, or even be using a client capable of consuming dbms_output messages.