Answer / gk

We can use Check constraint to restict the values of any
column.

Answer / suresh babu

create check constraint is the best way to restrict the
limited number of entries,because the constraint won't take
a separate space,but Trigger required separate memory
space.perhaps the trigger got error,it would affect all
entries in table.

Answer / guest

hint:using row level and statement level trigger

Answer / bikash khuntia

We have to create a trigger for that which is one of the
way for the solutuion as below:-

create or replace trigger trigger_name
before insert on table_name
for each row
DECLARE
v_count number;
begin
select count(apple) into v_count from table_name;
if v_count=100 then
raise_application_error('-20011','u cant insert more than
100 apples in the table');
end if;
end;

Answer / ashwin

You can create a sequence named seq_fruit as below .

create sequence seq_fruit
increment by 1
start with 1
maxvalue 100
minvalue 1
cycle
cache 10
if the current count ie currval of seq_fruit is 100 and
after this if u r inserting a new row in fruit table as
following

insert into fruit values(seq_fruit.nextval,30,40);
after the execution of this statement next value for apple
will be entered as 1 and not 101.

The cycle keyword will avoid the count of fruit column to go
beyond 100.

Answer / xyz

aLTER TABLE emp ADD CONSTRAINT C3 CHECK (EMPNO < 300)

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