After Inserting , Update / Insert into another table in pl/sql trigger I am working on PL/SQL trigger i have two table 

 TAG Table

SR.NO    ID    TAG    BRAND_ID  
------  ----  -----  ----------
  1      10    ABC       99


MY_TAGS Table

 SR_NO    TAG    COUNT   BRAND_ID  
--------   ---   ------   -------
   1      ABC       1      99


I need a trigger in such a way that 


If tag ABC is inserted  with BRAND_ID=99 one more times in TAG table then i need to increase the count of ABC to 2 in MY_TAGS table 
If new values inserted other than ABC for 99 then i need to insert new row in MY_TAG table 


How can I handle this situation using trigger. I am new to PL /SQL any help would be great.

I tried like this , but it will always execute Insert statement (i.e else part )

 CREATE or replace TRIGGER trig1
    AFTER INSERT ON TAG
    REFERENCING NEW AS newRow OLD AS oldRow
    FOR EACH ROW
    WHEN (newRow.ID &gt;=0)
    BEGIN
    IF(:newRow.TAG=:oldRow.TAG AND :newRow.BRAND_ID=:oldRow.BRAND_ID) THEN
       UPDATE MY_TAGS SET COUNT=(select max(counter) from MY_TAG)+1) where brand_id=newRow.BRAND_ID and tag=:newRow.TAG;
    ELSE
       INSERT INTO MY_TAGS VALUES((select max(SR_NO) from MY_TAGS)+1,:newRow.TAG,1,:newRow.BRAND_ID);
    END IF;
    END trig1;
Instead of materializing the count, which bears the risk of inconsistencies, I recommend you drop the my_tags table and create a view which uses aggregation to get the count.

DROP TABLE my_tags;

CREATE VIEW my_tags
AS
SELECT sr_no,
       tag,
       brand_id,
       count(*)
       FROM tag
       GROUP BY sr_no,
                tag,
                brand_id;


Like that you don't need any trigger, the count is always accurately calculated.