Day 5 of MySQL learning

create table `tb_result` (
  `rq` date not null,
  `sf` char(1) not null
) engine=innodb;

insert into `tb_result` values 
    ('2017-04-09',' - '),
    ('2017-04-09',' - '),
    ('2017-04-09',' negative '),
    ('2017-04-09',' negative '),
    ('2017-04-10',' - '),
    ('2017-04-10',' negative '),
    ('2017-04-10',' - ');

--  Use the above table to query the results as shown below .
-- | date       | win  | los  |
-- | ---------- | ---- | ---- |
-- | 2017-04-09 | 2    | 2    |
-- | 2017-04-10 | 2    | 1    |

select 
	rq as `date`,
    sum(case sf when ' - ' then 1 else 0 end) as win,
    sum(case sf when ' negative ' then 1 else 0 end) as los
from tb_result
group by rq;

create table `tb_course`
(
`course_id` int unsigned not null comment ' Course number ',
`course_name` varchar(50) not null comment ' Course name ',
primary key (`course_id`)
) engine=innodb;

insert into `tb_course` values 
    (1, 'Python'),
    (2, 'Java'),
    (3, 'Database'),
    (4, 'JavaScript');

drop table if exists `tb_open_date`;

create table `tb_open_date`
(
`month` char(6) not null comment ' Opening date ',
`course_id` int unsigned not null comment ' Course number '
) engine=innodb;

insert into `tb_open_date` values
    ('202106', 1),
    ('202106', 3),
    ('202106', 4),
    ('202107', 4),
    ('202108', 2),
    ('202108', 4);

--  Use the above table to query the results as shown below .
-- | course_name | Jun | Jul | Aug |
-- | ----------- | --- | --- | --- |
-- | Python      |  o  |  x  |  x  |
-- | Java        |  x  |  x  |  o  |
-- | Database    |  o  |  x  |  x  |
-- | JavaScript  |  o  |  o  |  o  |

select 
    `course_name`,
    case when exists (
        select 'x' from `tb_open_date` as t2
        where t1.`course_id`=t2.`course_id` and `month`='202106'
    ) then 'o' else 'x' end as Jun, 
    case when exists (
        select 'x' from `tb_open_date` as t2
        where t1.`course_id`=t2.`course_id` and `month`='202107'
    ) then 'o' else 'x' end as Jul, 
    case when exists (
        select 'x' from `tb_open_date` as t2
        where t1.`course_id`=t2.`course_id` and `month`='202108'
    ) then 'o' else 'x' end as Aug
from `tb_course` as t1;

create database homework default charset utf8mb4;

use homework;

create table tb_product
(
prod_id varchar(50) not null comment ' Commodity number ',
category varchar(50) not null comment ' species ',
color varchar(10) not null comment ' Color ',
weight decimal(10, 2) not null comment ' weight ',
price integer not null comment ' Price ',
primary key (prod_id)
) engine=innodb comment ' Product list ';

insert into tb_product values 
    ('prodA', 'cateA', 'yellow', 5.6, 100),
    ('prodB', 'cateB', 'red', 3.7, 200),
    ('prodC', 'cateC', 'blue', 10.3, 300),
    ('prodD', 'cateD', 'black', 7.8, 400);

create table tb_order
(
id integer not null auto_increment,
order_no varchar(20) not null comment ' The order number ',
user_id varchar(50) not null comment ' The user no. ',
order_date date not null comment ' Order date ',
store varchar(50) not null comment ' Shop number ',
product varchar(50) not null comment ' Commodity number ',
quantity integer not null comment ' Purchase quantity ',
primary key (id)
) engine=innodb comment ' The order sheet ';

insert into tb_order 
    (order_no, user_id, order_date, store, product, quantity) 
values 
    ('D001', 'customerA', '2018-01-01', 'storeA', 'prodA', 1),
    ('D001', 'customerA', '2018-01-01', 'storeA', 'prodB', 1),
    ('D001', 'customerA', '2018-01-01', 'storeA', 'prodC', 1),
    ('D002', 'customerB', '2018-01-12', 'storeB', 'prodB', 1),
    ('D002', 'customerB', '2018-01-12', 'storeB', 'prodD', 1),
    ('D003', 'customerC', '2018-01-12', 'storeC', 'prodB', 1),
    ('D003', 'customerC', '2018-01-12', 'storeC', 'prodC', 1),
    ('D003', 'customerC', '2018-01-12', 'storeC', 'prodD', 1),
    ('D004', 'customerA', '2018-01-01', 'storeD', 'prodD', 2),
    ('D005', 'customerB', '2018-01-23', 'storeB', 'prodA', 1);

create table tb_store
(
store_id varchar(50) not null comment ' Shop number ',
city varchar(20) not null comment ' City ',
primary key (store_id)
) engine=innodb comment ' Shop list ';

insert into tb_store values 
    ('storeA', 'cityA'),
    ('storeB', 'cityA'),
    ('storeC', 'cityB'),
    ('storeD', 'cityC'),
    ('storeE', 'cityD'),
    ('storeF', 'cityB');

--  Find out that the total purchase amount is not less than 800 User number of user 、 Total purchase amount 、 Total orders and total purchases , If the order number is the same, it will be counted as one order .
select 
	user_id, 
    sum(price*quantity) as  Total purchase amount ,
    count(distinct order_no) as  Total order number ,
    sum(quantity) as  Total number of goods purchased 
from tb_order, tb_product 
where product=prod_id 
group by user_id
having  Total purchase amount >=800;

select 
	user_id,
    sum(price*quantity) as  Total purchase amount ,
    count(distinct order_no) as  Total order number ,
    sum(quantity) as  Total number of goods purchased 
from (
	select user_id, price, quantity, order_no 
	from tb_order inner join tb_product 
	on product=prod_id
) temp 
group by user_id 
having  Total purchase amount >=800;

--  Find out all the cities （ Including cities without purchase records ） The number of head offices , Total number of buyers and total purchase amount .
select 
	city,
    count(distinct store_id) as  Number of head office stores ,
    count(distinct user_id) as  Total number of buyers ,
    coalesce(sum(price*quantity), 0) as  Total purchase amount 
from tb_store 
left outer join tb_order on store=store_id
left outer join tb_product on product=prod_id
group by city;

--  Find out if you have bought "cateA" Users of products and their average order amount , If the order number is the same, it will be counted as one order .
select 
	user_id,
    sum(price*quantity) / count(distinct order_no) as  Average order amount 
from tb_order, tb_product 
where product=prod_id and user_id in (
	select 
		distinct user_id
	from tb_order, tb_product 
	where product=prod_id and category='cateA'
)
group by user_id;