In sqlite

create table users ( email char(20), name char(16), pwd char(4), city char(15), gender char(1), primary key (email) ); create table products ( pid char(4), descr char(20), primary key (pid) ); create table sales ( sid char(4), lister char(20) not null, pid char(4), edate date, descr char(25), cond char(10), rprice int, primary key (sid), foreign key (lister) references users, foreign key (pid) references products ); create table bids ( bid char(20), bidder char(20) not null, sid char(4) not null, bdate date, amount float, primary key (bid), foreign key (bidder) references users, foreign key (sid) references sales ); create table items ( sid char(4), no int, pid char(4), descr char(25), primary key (sid,no), foreign key (sid) references sales on delete cascade, foreign key (pid) references products ); create table reviews ( reviewer char(20), reviewee char(20), rating float, rtext char(20), rdate date, primary key (reviewer, reviewee), foreign key (reviewer) references users, foreign key (reviewee) references users ); create table previews ( rid int, pid char(4), reviewer char(20) not null, rating float, rtext char(20), rdate date, primary key (rid), foreign key (pid) references products, foreign key (reviewer) references users ); create table endorses ( rid int, endorser char(20), primary key (rid, endorser), foreign key (rid) references previews, foreign key (endorser) references users );

Question:

Create a view called product_info with columns pid, descr, revcnt, rating, rating6, and salecnt. The view includes for each product the product id, the description, the number of reviews, the average rating, the average rating based on the reviews written within the past 6 months, and the number of different sales that are either associated to the product or have an item that is associated to the product. Include products with no reviews or sales in the output with zero counts (if applicable) or null values.