Question { MasterCard, 2717 }

t1
col1 col2
nishi 5000
lucky 6700
akash 7000
i want that a query that when i insert 7000 it will show me data already present and data will not insert. if data is not present it will insert.

Answer

The best thing would be to create a trigger which checks and not allows duplicate data .

Create or replace trigger trig1
before insert or update on t1
for each row
declare
a number (10);
begin
select count(*) into a from t1 where col2 = :new.col2;
if a >= 1 then
raise_application_error(-20123,'data already present and data will not insert');
elsif a = 0 then
dbms_output.put_line('inserted');
end if;
end;