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using/invoking trigger

Posted on 2012-04-11
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Last Modified: 2012-04-30
hi guys

In ORacle SQL Developer i see few triggers under the Triggers folder.

The goal of our trigger is to create a a new primary key which is stored in prod_id


create or replace TRIGGER prodschema.prod_ins_id
BEFORE
   INSERT ON prodschema.product
    FOR EACH ROW WHEN (NEW.prod_id IS NULL)
 
        BEGIN
        
          SELECT seq_prod_id.NEXTVAL   -- seq_prod_id is a sequence
                 , 'PROD_CODE' || seq_prod_id.CURRVAL
                 
          INTO  :NEW.prod_id
            , :NEW.prod_code
              
          FROM DUAL;
END;


what i want to know is we have a insert store procedure which inserts rows into the product  table. when this insert procedure is invoked, is the above trigger automatically called ?

I would also like to know what precautions to take when writing and invoking a trigger.

thanks
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Question by:royjayd
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by:slightwv (䄆 Netminder)
slightwv (䄆 Netminder) earned 800 total points
ID: 37832761
>>is the above trigger automatically called ?

If the procedure does an insert into that table, then yes the trigger will fire.

>>I would also like to know what precautions to take when writing and invoking a trigger.

There is a large debate on this topic if you search around:
http://www.dba-oracle.com/m_trigger.htm
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by:
sujith80 earned 1200 total points
ID: 37832813
The trigger will fire automatically as long as it is ENABLED and VALID

To check if it is ENABLED run the below

select trigger_name, status, ut.*
from all_triggers ut
where owner = 'PRODSCHEMA'
trigger_name = upper('prod_ins_id');

to check the status
select status, ao.*
from all_objects ao
where owner = 'PRODSCHEMA'
and object_name = 'PROD_INS_ID'

>> what precautions to take when writing and invoking a trigger
Few of them
- if there are multiple triggers you need to take care of the sequencing of triggers
- Try to avoid complicated logic
- Try to avoid cross referencing of objects in triggers, this often leads to deadlocks
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