题目内容

夜校教务要把「指定夜校里真正动过笔的学员」按题目档位拆开，看人均作答条数。库里有三张表：学员卡、作答流水、题目档位。卡号、校区名、档位英文、对错标记都按表里的原文使用。

本次只统计校区为 海风夜校 的学员。先筛出该校区，再把流水和档位对上。某个档位上的人均作答条数定义为：该校学员在该档位上的流水总条数，除以「在该档位上至少有一条流水的该校学员人数」。该校完全没有作答的档位不输出。平均值小数点后保留 4 位，第 5 位四舍五入。

学员卡：trainee_card

pad_id 是手写板编号，campus 是夜校校区。只有 8801、8802 属于海风夜校。

作答流水：drill_flow

result 只有 right / wrong。完整流水见输入里的 INSERT。

题目档位：drill_item

grade 只有 hard / medium / easy。

查询应返回：

输入描述

输入是一段可执行的 SQL：创建 trainee_card、drill_flow、drill_item 并写入示例行。表名、字段名、校区中文名、male/female、right/wrong、hard/medium/easy 均须按原文使用。

输出描述

输出若干行，每行三个字段，用 | 分隔：校区、档位、人均作答条数（四位小数，外加括号）。只输出海风夜校、且该校确有作答的档位。

样例1

输入

drop table if exists `trainee_card`;
drop table if exists `drill_flow`;
drop table if exists `drill_item`;
CREATE TABLE `trainee_card` (
`id` int NOT NULL,
`pad_id` int NOT NULL,
`gender` varchar(14) NOT NULL,
`age` int ,
`campus` varchar(32) NOT NULL,
`gpa` float,
`active_days_within_30` int ,
`question_cnt` int ,
`answer_cnt` int
);
CREATE TABLE `drill_flow` (
`id` int NOT NULL,
`pad_id` int NOT NULL,
`item_id` int NOT NULL,
`result` varchar(32) NOT NULL
);
CREATE TABLE `drill_item` (
`id` int NOT NULL,
`item_id` int NOT NULL,
`grade` varchar(32) NOT NULL
);

INSERT INTO trainee_card VALUES(1,7001,'male',22,'江左书院',3.1,6,2,8);
INSERT INTO trainee_card VALUES(2,7002,'female',24,'青禾学堂',3.7,11,4,16);
INSERT INTO trainee_card VALUES(3,8801,'male',26,'海风夜校',3.5,18,12,40);
INSERT INTO trainee_card VALUES(4,7004,'female',21,'江左书院',3.0,4,1,3);
INSERT INTO trainee_card VALUES(5,8802,'male',29,'海风夜校',3.2,14,6,20);
INSERT INTO trainee_card VALUES(6,7006,'female',23,'星河夜校',3.9,9,5,22);

INSERT INTO drill_flow VALUES(1,7001,501,'wrong');
INSERT INTO drill_flow VALUES(2,7002,502,'wrong');
INSERT INTO drill_flow VALUES(3,7002,501,'wrong');
INSERT INTO drill_flow VALUES(4,7001,504,'right');
INSERT INTO drill_flow VALUES(5,7004,506,'right');
INSERT INTO drill_flow VALUES(6,7004,505,'right');
INSERT INTO drill_flow VALUES(7,7004,503,'wrong');
INSERT INTO drill_flow VALUES(8,8801,503,'wrong');
INSERT INTO drill_flow VALUES(9,8801,502,'wrong');
INSERT INTO drill_flow VALUES(10,8802,501,'right');
INSERT INTO drill_flow VALUES(11,8801,501,'wrong');
INSERT INTO drill_flow VALUES(12,7004,506,'right');
INSERT INTO drill_flow VALUES(13,7004,505,'right');
INSERT INTO drill_flow VALUES(14,7004,503,'wrong');
INSERT INTO drill_flow VALUES(15,8801,503,'wrong');
INSERT INTO drill_flow VALUES(16,8801,502,'wrong');
INSERT INTO drill_flow VALUES(17,8802,501,'right');
INSERT INTO drill_flow VALUES(18,8801,501,'wrong');
INSERT INTO drill_flow VALUES(19,7004,503,'wrong');
INSERT INTO drill_flow VALUES(20,8801,503,'wrong');
INSERT INTO drill_flow VALUES(21,8801,502,'wrong');
INSERT INTO drill_flow VALUES(22,8802,501,'right');
INSERT INTO drill_flow VALUES(23,8801,501,'wrong');

输出

海风夜校|easy|(4.5000)
海风夜校|medium|(3.0000)

说明

海风夜校只有手写板 8801、8802。

• 8801：501（easy）3 条，502（medium）3 条，503（easy）3 条。
• 8802：501（easy）3 条。

easy 共 9 条、有作答学员 2 人，人均 $9/2=(4.5000)$；medium 共 3 条、有作答学员只有 8801 共 1 人，人均 $3/1=(3.0000)$。hard 该校没有流水，不输出。