How can i avoid null value of:old or new? Im trying to insert to one table 3 step before update,delete,insert with having more columns
How can i avoid null value of:old or new?
Both old
and new
pseudorecords reflect values in the table (old ones are "previous", new ones are... well, "new", which will replace old ones).
Suppose there's a job
column in the table and its value is NULL
. If you run
update emp set job = 'CLERK' where empno = 7369;
then :old.job = NULL
, :new.job = 'CLERK'
.
Or, the opposite : suppose there was 'ANALYST' in that column and you run
update emp set job = null where empno = 7369;
so :old.job = 'ANALYST'
, :new.job = NULL
.
You asked how to avoid null
; why would you want to "avoid" them? They have values they should have. There's nothing wrong in NULL
as it means that there's an absence of a value.
In the 1st example above (where :old.job = null
), what would you want to use instead of it? There was no value there...
If you must (although, I don't know why), you could use NVL
or COALESCE
functions or CASE
expression; for example:
insert into log_table (job) values (nvl(:old.job, 'no previous job'));
insert into log_table (job) values (coalesce(:old.job, 'no previous job'));
insert into log_table (job), values (case when :old.job is null then 'no previous job'
else :old.job
end);
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