Mysql中根据不同条件来统计、汇总数据的操作实例

mysql> create database shopping;    # 创建数据库
mysql> use shopping;    # 使用数据库

mysql> create table orders(
    -> id int(11) primary key not null comment '订单编号',
    -> category varchar(255) default null comment '分类',
    -> status varchar(2) default null comment '状态(0:创建,1:待付款,2:待发货,3:待收货)',
    -> amount decimal(10,2) default null comment '金额');

mysql> insert into orders values (0, '华为', '0', 5500.00);
mysql> insert into orders values (1, '小米', '2', 3000.00);
mysql> insert into orders values (2, '华为', '1', 5500.00);
mysql> insert into orders values (3, '苹果', '2', 5000.00);
mysql> insert into orders values (4, '华为', '1', 5500.00);
mysql> insert into orders values (5, '小米', '2', 3000.00);
mysql> insert into orders values (6, '华为', '0', 5500.00);
mysql> insert into orders values (7, '苹果', '1', 5000.00);
mysql> insert into orders values (8, '小米', '3', 3000.00);
mysql> insert into orders values (9, '华为', '3', 5500.00);

select * from orders;

mysql> select
    -> count(case when status = '0' then 1 else null end ) as 创建,  
    -> count(case when status = '1' then 1 else null end ) as 待付款,
    -> count(case when status = '2' then 1 else null end ) as 待发货,
    -> count(case when status = '3' then 1 else null end ) as 待收货 
    -> from orders;

mysql> select
    -> count(case when status = '0' then 1 else null end ) as 创建, 
    -> count(case when status = '1' then 1 else null end ) as 待付款,
    -> count(case when status = '2' then 1 else null end ) as 待发货,
    -> count(case when status = '3' then 1 else null end ) as 待收货,
    -> sum(case when status = '0' then ifnull(amount,0) else 0 end) as 创建总金额,
    -> sum(case when status = '1' then ifnull(amount,0) else 0 end) as 待付款总金额, 
    -> sum(case when status = '2' then ifnull(amount,0) else 0 end) as 待发货总金额,
    -> sum(case when status = '3' then ifnull(amount,0) else 0 end) as 待收货总金额  
    -> from orders;

mysql> select category as 分类,
    -> count(case when status = '0' then 1 else null end ) as 创建, 
    -> count(case when status = '1' then 1 else null end ) as 待付款,
    -> count(case when status = '2' then 1 else null end ) as 待发货,
    -> count(case when status = '3' then 1 else null end ) as 待收货,
    -> sum(case when status = '0' then ifnull(amount,0) else 0 end) as 创建总金额,
    -> sum(case when status = '1' then ifnull(amount,0) else 0 end) as 待付款总金额,
    -> sum(case when status = '2' then ifnull(amount,0) else 0 end) as 待发货总金额,
    -> sum(case when status = '3' then ifnull(amount,0) else 0 end) as 待收货总金额  
    -> from orders group by category;

mysql> select * ,
    -> (case when amount<= 3000 then '低' 
    -> when amount<= 5000 then '中'
    -> when amount<= 10000 then '高'
    -> else '未知区间' end) as 价格等级 
    -> from orders;