Dynamic query with :new value - sql

Question

I have a table called PKCHANGES that has a few columns, one of which is the primary_key column. What I want is to create a trigger on other tables, and upon an insert I grab some values and post them to the PKCHANGES table. All is fine except for when I try and post the primary key values. I want that in the column primary_key I input the primary key values comma delimited. So if TableX has 3 primary keys, in PKCHANGES (primary_key column) I post value1,value2,value3.
So far I am only managing to get the below as a result and not the actual values
":new.pkCol1:new.pkCol2:new.pkCol3"
My pl/sql block is:
DECLARE
mySql varchar2(5000);
myTable varchar2(10) := 'TableX';
BEGIN
mySql := 'CREATE OR REPLACE TRIGGER ' || 't_1' || ' AFTER INSERT ON ' || myTable || '
FOR EACH ROW
DECLARE
currentPK varchar2(200); --Contains the current primary key value in the loop
result varchar2(200); --Contains the appended string of primary key values
--Cursor that contains primaryKeys for table
CURSOR pks IS
SELECT cols.column_name FROM all_constraints cons, all_cons_columns cols
WHERE cons.constraint_type = ''P''
AND cons.constraint_name = cols.constraint_name
AND cons.table_name = ' || '''' || myTable || '''' || ';
BEGIN
--Loop through primary keys, get the value from the trigger, and append the string.
for current_pk IN pks LOOP
BEGIN
currentPK := '':new.'' || current_pk.column_name;
result:= result || currentPK;
END;
END LOOP;'
||
' --Insert the appended values into the primary_key column
INSERT INTO PKCHANGES(primary_key)' ||
'VALUES (result);'
|| ' END;';
dbms_output.put_line(mySql);
EXECUTE IMMEDIATE mySql;
END;
Any idea?

Answer 1

The primary key of the TableX need not be queried on each insert. It is stable and if once changed, you will change the trigger as well.
This allows you to pop up the logic out of the trigger.
In the first step concatenate the PK. I'd prefer LISTAGG as it handels elegant the delimiter. You get something like :new.COL1||','||:new.COL2||','||:new.COL3
Also make sure the table name is in correct case (I asume upper case; otherwise you need to quote the name).
In the next step generate the trigger, that will basicaly contain only the INSERT
DECLARE
mySql varchar2(5000);
myTable varchar2(10) := 'TableX';
result varchar2(200); -- Contains the concatenated string of primary key column names with delimiters,
-- e.g. ":new.COL1||','||:new.COL2||','||:new.COL3"
BEGIN
SELECT listagg(':new.'||cols.column_name,'||'',''||') within group (order by position) into result
FROM all_constraints cons, all_cons_columns cols
WHERE cons.constraint_type = 'P'
AND cons.constraint_name = cols.constraint_name
AND cons.table_name = upper(myTable);
mySql := 'CREATE OR REPLACE TRIGGER ' || 't_1' || ' AFTER INSERT ON ' || myTable || '
FOR EACH ROW
BEGIN
--Insert the appended values into the primary_key column
INSERT INTO PKCHANGES(primary_key)' ||
'VALUES ('||result||');'
|| ' END;';
dbms_output.put_line(mySql);
EXECUTE IMMEDIATE mySql;
END;
/
Test
create table TableX
(col1 number,
col2 number,
col3 number,
col4 number);
alter table TableX add (primary key (col1, col2, col3));
insert into TableX values (1,2,3,4);
select * from PKCHANGES;
PRIMARY_KEY
-----------
1,2,3