Trigger to concatenate two fields in a table

Question

Hi
I am trying to concatenate two column in a table and add to the third column in the same table, all the columns are
numbers, I want to write a trigger which is after insert to do that..does anyone know how its done...
thanks a lot
Jessica

Answer 1

Hi, Jessica,
Welcome to the forum!
Do you really need to store this concatenation? The way you would get these results in a normalized database is to store the numbers separately, and comnbine them, when necessary, in queries and reports. You can use use a view to avoid repeating the same coiding over and over.
If you really want to store the value, use a BEFORE INSERT OR UPDATE trigger, like this:
CREATE OR REPLACE TRIGGER     table_x_biu
BEFORE     INSERT OR UPDATE
ON     table_x
FOR EACH ROW
BEGIN
     :NEW.column_3 := TO_CHAR (:NEW.column_1)
                || '-'
                || TO_CHAR (:NEW.column_2);
END;I'm confused by your exact requirements. Concatentaion can only be done to strings.
If column_1 and column_2 are NUMBERs, the trigger above will make string versions of those numbers, concatenate them together (with a hyphen between them), and put the results in the VARCHAR2 column column_3.
So after this statement:
INSERT INTO  table_x (column_1, column_2, column_3)
       VALUES          (1,     2,       '9-8');the new row will have column_3= '1-2'. (In this case, there is no point in explicitly setting column_3, because the trigger will always set the value based entirely on column_1 and column_2.)
If you need more help, post CREATE TABLE , INSERT and UPDATE statements, and who what you want the table to contain after each INSERT or UPDATE.