create table Purchase_order_header(pono number(10) primary 

key,po_date date not null,supplier_no number(10) not 

null,total_amount number(9,2) not null);

create table Purchase_order_Detail(pono number(10) references 

Purchase_order_header,item_no number(10) not null,item_name 

varchar(20) not null,qty_rate number(7,2) not null);

2:alter table Purchase_order_header add(excepted_delivery_date 

date);
3:select qty*rate as total from Purchase_order_Detail1;
4:select to_char(po_date,'ddth mon yy day') from 

Purchase_order_header;
5:select count(distinct(supplier_no)) from Purchase_order_header;
6:select item_name from Purchase_order_Detail1 where item_name 

like '%m%'
7:
8:select a.* from Purchase_order_header a,Purchase_order_header b 

where to_char(a.EXCEPTED_DELIVERY_DATE,'MON')= 

to_char(b.po_date,'MON');