extra.sql.txt

------showing the current user name
show user; 



drop table basic_table;
declare
   a int;
begin
   select count(*) into a from user_tables where table_name = upper('basic_table');
EXCEPTION
    WHEN no_data_found THEN
        a := 0;
if (a = 1) then
      execute immediate q'[drop table basic_table]'; -- executing the command drop table
end if;
end;
/

create table basic_table (
  d_roll integer,
  d_mark integer
);


-------------proper example of how the transaction actually works for a single user

insert into basic_table values (1,90);

insert into basic_table values (2,95);
commit;
insert into basic_table values (3,84);
SAVEPOINT x_save;
insert into basic_table values (4,75);

insert into basic_table values (5,86);

SAVEPOINT y_save;
insert into basic_table values (6,97);

select * from basic_table;
rollback to x_save;
select *from basic_table;
delete from basic_table;
select *from basic_table;
rollback;



drop table dummy;
create table dummy (
emp_name varchar(20),
 joining date
);
insert into dummy values ('wahida',TO_DATE('17-JUN-1987', 'dd-MON-yyyy')); 
select LAST_DAY (joining) from dummy;

SELECT emp_name, EXTRACT(Month FROM joining) AS Month
FROM dummy;


select sysdate from dual;
select current_date from dual;
select systimestamp from dual;

SELECT LEAST (TO_DATE ('22-DEC-2007'),TO_DATE ('12-DEC-2008'))
FROM dual;
SELECT GREATEST (TO_DATE ('22-DEC-2007'),TO_DATE ('12-DEC2008')) 
from dual;