# 学生管理系统 — 数据库设计文档

## 1. 数据库概述

| 属性 | 说明 |
|------|------|
| 数据库名 | `sms`（学生管理系统 Student Manage System） |
| 存储引擎 | InnoDB |
| 字符集 | utf8mb4 |
| 默认排序规则 | utf8mb4_unicode_ci |
| 通用字段方案 | `id`、`create_time`、`update_time`、`is_deleted`、`delete_time` |

---

## 2. ER 关系图

```
┌──────────────────┐       ┌──────────────────┐       ┌──────────────────┐
│     teachers     │       │     classes      │       │    students      │
├──────────────────┤       ├──────────────────┤       ├──────────────────┤
│ id (PK)          │       │ id (PK)          │       │ id (PK)          │
│ num (UK)         │       │ num (UK)         │       │ num (UK)         │
│ name             │  1:N  │ name             │  1:N  │ name             │
│ age              │ ----> │ class_start_time │ ----> │ age              │
│ sex              │       │                  │       │ sex              │
│ home_place       │       │ head_teacher_id  │       │ home_place       │
│ college          │       │ coach_teacher_id │       │ college          │
│ specialty        │       │ tutor_teacher_id │       │ specialty        │
│ enrollment_time  │       └──────┬───────────┘       │ enrollment_time  │
│ graduate_time    │                                  │ graduate_time    │
│ education        │                                  │ education        │
│ work_experience  │                                  │                  │
│ coach_area       │                                  │ create_time      │
│                  │                                  │ update_time      │
│ create_time      │                ------------------│ is_deleted       │
│ update_time      │               │                  │ delete_time      │
│ is_deleted       │               │ 1:N              └──────────────────┘
│ delete_time      │               ▼                         | 1:1
└──────────────────┘       ┌──────────────────┐       ┌──────────────────┐
                           │      scores      │       │   employment     │
                           ├──────────────────┤       ├──────────────────┤
                           │ id (PK)          │       │ id (PK)          │
                           │ sid (FK→students)│       │ sid (FK→students)│
                           │ num              │       │ class_id (FK)    │
                           │ score            │       │ employment_open  │
                           │                  │       │  _time           │
                           │ create_time      │       │ offer_recived    │
                           │ update_time      │       │  _time           │
                           │ is_deleted       │       │ employment_comp  │
                           │ delete_time      │       │  any             │
                           └──────────────────┘       │ employment_salar │
                                                      │  y               │
                                                      │                  │
                                                      │ create_time      │
                                                      │ update_time      │
                                                      │ is_deleted       │
                                                      │ delete_time      │
                                                      └──────────────────┘
```

---

## 3. 表结构详述

### 3.1 teachers — 教师表

| 字段名 | 类型 | 约束 | 说明 |
|--------|------|------|------|
| id | INT | PK, AUTO_INCREMENT | 主键 |
| num | VARCHAR(30) | UNIQUE, NOT NULL, INDEX | 教师编号 |
| name | VARCHAR(30) | NOT NULL | 姓名 |
| age | INT | DEFAULT 18 | 年龄 |
| sex | INT | DEFAULT 0 | 性别：0未知 1男 2女 |
| home_place | VARCHAR(50) | NULL | 家乡 |
| college | VARCHAR(50) | NULL | 毕业院校 |
| specialty | VARCHAR(50) | NULL | 专业 |
| enrollment_time | DATETIME | NULL | 入学时间 |
| graduate_time | DATETIME | NULL | 毕业时间 |
| education | VARCHAR(50) | NULL | 学历 |
| work_experience | TEXT | NULL | 工作经验 |
| coach_area | VARCHAR(50) | NULL | 教学方向：应用/项目/算法 |
| create_time | DATETIME | NOT NULL | 创建时间 |
| update_time | DATETIME | NOT NULL | 更新时间 |
| is_deleted | BOOLEAN | DEFAULT FALSE | 软删除标志 |
| delete_time | DATETIME | NULL | 删除时间 |

**索引：**
```sql
PRIMARY KEY (id),
UNIQUE KEY uk_tnum (num),
KEY idx_num (num)
```

**外键：** 无（teachers 作为被引用方）

---

### 3.2 classes — 班级表

| 字段名 | 类型 | 约束 | 说明 |
|--------|------|------|------|
| id | INT | PK, AUTO_INCREMENT | 主键 |
| num | VARCHAR(30) | UNIQUE, NOT NULL, INDEX | 班级编号 |
| name | VARCHAR(30) | NOT NULL | 班级名称 |
| class_start_time | DATETIME | NULL | 开课时间 |
| head_teacher_id | INT | NULL, FK→teachers.id | 班主任 ID |
| coach_teacher_id | INT | NULL, FK→teachers.id | 授课老师 ID |
| tutor_teacher_id | INT | NULL, FK→teachers.id | 助教老师 ID |
| create_time | DATETIME | NOT NULL | 创建时间 |
| update_time | DATETIME | NOT NULL | 更新时间 |
| is_deleted | BOOLEAN | DEFAULT FALSE | 软删除标志 |
| delete_time | DATETIME | NULL | 删除时间 |

**索引：**
```sql
PRIMARY KEY (id),
UNIQUE KEY uk_class_num (num),
KEY idx_head_teacher (head_teacher_id),
KEY idx_coach_teacher (coach_teacher_id),
KEY idx_tutor_teacher (tutor_teacher_id)
```

**外键：**
```sql
CONSTRAINT fk_classes_head_teacher  FOREIGN KEY (head_teacher_id)  REFERENCES teachers(id) ON DELETE SET NULL ON UPDATE CASCADE,
CONSTRAINT fk_classes_coach_teacher FOREIGN KEY (coach_teacher_id) REFERENCES teachers(id) ON DELETE SET NULL ON UPDATE CASCADE,
CONSTRAINT fk_classes_tutor_teacher FOREIGN KEY (tutor_teacher_id) REFERENCES teachers(id) ON DELETE SET NULL ON UPDATE CASCADE
```

---

### 3.3 students — 学生表

| 字段名 | 类型 | 约束 | 说明 |
|--------|------|------|------|
| id | INT | PK, AUTO_INCREMENT | 主键 |
| num | VARCHAR(30) | UNIQUE, NOT NULL, INDEX | 学生编号 |
| name | VARCHAR(30) | NOT NULL | 姓名 |
| age | INT | DEFAULT 18 | 年龄 |
| sex | INT | DEFAULT 0 | 性别：0未知 1男 2女 |
| home_place | VARCHAR(50) | NULL | 家乡 |
| college | VARCHAR(50) | NULL | 毕业院校 |
| specialty | VARCHAR(50) | NULL | 专业 |
| enrollment_time | DATETIME | NULL | 入学时间 |
| graduate_time | DATETIME | NULL | 毕业时间 |
| education | VARCHAR(50) | NULL | 学历 |
| class_id | INT | NOT NULL, DEFAULT 0, INDEX | 所属班级 ID |
| advisor_id | INT | NULL, FK→teachers.id | 顾问老师 ID |
| create_time | DATETIME | NOT NULL | 创建时间 |
| update_time | DATETIME | NOT NULL | 更新时间 |
| is_deleted | BOOLEAN | DEFAULT FALSE | 软删除标志 |
| delete_time | DATETIME | NULL | 删除时间 |

**索引：**
```sql
PRIMARY KEY (id),
UNIQUE KEY uk_snum (num),
KEY idx_class_id (class_id),
KEY idx_advisor_id (advisor_id),
KEY idx_class_deleted (class_id, is_deleted)  -- 复合索引，优化班级学生列表查询
```

**外键：**
```sql
CONSTRAINT fk_students_class   FOREIGN KEY (class_id)   REFERENCES classes(id)  ON DELETE RESTRICT  ON UPDATE CASCADE,
CONSTRAINT fk_students_advisor FOREIGN KEY (advisor_id) REFERENCES teachers(id) ON DELETE SET NULL ON UPDATE CASCADE
```

> **注意**：`class_id` 使用 `ON DELETE RESTRICT`，防止误删有学生的班级。

---

### 3.4 scores — 成绩表

| 字段名 | 类型 | 约束 | 说明 |
|--------|------|------|------|
| id | INT | PK, AUTO_INCREMENT | 主键 |
| sid | INT | NOT NULL, FK→students.id, INDEX | 学生 ID |
| num | VARCHAR(30) | NOT NULL | 考核序次（如"第一次考核"） |
| score | DECIMAL(10,2) | NOT NULL | 分数 |
| create_time | DATETIME | NOT NULL | 创建时间 |
| update_time | DATETIME | NOT NULL | 更新时间 |
| is_deleted | BOOLEAN | DEFAULT FALSE | 软删除标志 |
| delete_time | DATETIME | NULL | 删除时间 |

**索引：**
```sql
PRIMARY KEY (id),
UNIQUE KEY uk_sid_score (sid, num),  -- 防止同一学生同一考核重复录入
KEY idx_sid (sid)
```

**外键：**
```sql
CONSTRAINT fk_scores_student FOREIGN KEY (sid) REFERENCES students(id) ON DELETE CASCADE ON UPDATE CASCADE
```

> 删除学生时，其所有成绩记录自动级联删除。

---

### 3.5 employment — 就业表

| 字段名 | 类型 | 约束 | 说明 |
|--------|------|------|------|
| id | INT | PK, AUTO_INCREMENT | 主键 |
| sid | INT | UNIQUE, FK→students.id | 学生 ID（一对一） |
| class_id | INT | NOT NULL, INDEX | 所属班级 ID |
| employment_open_time | DATETIME | NULL | 就业开放时间 |
| offer_recived_time | DATETIME | NULL | Offer 下发时间 |
| employment_company | VARCHAR(50) | NULL | 就业公司 |
| employment_salary | DECIMAL(20,5) | NULL | 就业薪资（月薪） |
| create_time | DATETIME | NOT NULL | 创建时间 |
| update_time | DATETIME | NOT NULL | 更新时间 |
| is_deleted | BOOLEAN | DEFAULT FALSE | 软删除标志 |
| delete_time | DATETIME | NULL | 删除时间 |

**索引：**
```sql
PRIMARY KEY (id),
UNIQUE KEY uk_sid (sid),           -- 一名学生只允许一条就业记录
KEY idx_class_id (class_id),
KEY idx_class_deleted (class_id, is_deleted)  -- 复合索引，优化班级就业统计
```

**外键：**
```sql
CONSTRAINT fk_employment_student FOREIGN KEY (sid)     REFERENCES students(id) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT fk_employment_class   FOREIGN KEY (class_id) REFERENCES classes(id)  ON DELETE RESTRICT  ON UPDATE CASCADE
```

---

## 4. 完整 DDL（可直接执行）

```sql
CREATE DATABASE IF NOT EXISTS sms
  CHARACTER SET utf8mb4
  COLLATE utf8mb4_unicode_ci;

USE sms;

-- ==================== teachers ====================
CREATE TABLE IF NOT EXISTS teachers (
    id            INT AUTO_INCREMENT PRIMARY KEY,
    num           VARCHAR(30)  NOT NULL COMMENT '教师编号',
    name          VARCHAR(30)  NOT NULL DEFAULT '' COMMENT '姓名',
    age           INT          NOT NULL DEFAULT 18 COMMENT '年龄',
    sex           INT          NOT NULL DEFAULT 0  COMMENT '性别：0未知 1男 2女',
    home_place    VARCHAR(50)  NULL     COMMENT '家乡',
    college       VARCHAR(50)  NULL     COMMENT '毕业院校',
    specialty     VARCHAR(50)  NULL     COMMENT '专业',
    enrollment_time DATETIME   NULL     COMMENT '入学时间',
    graduate_time  DATETIME   NULL     COMMENT '毕业时间',
    education     VARCHAR(50)  NULL     COMMENT '学历',
    work_experience TEXT      NULL     COMMENT '工作经验',
    coach_area    VARCHAR(50)  NULL     COMMENT '教学方向：应用/项目/算法',
    create_time   DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP,
    update_time   DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    is_deleted    TINYINT(1)   NOT NULL DEFAULT 0,
    delete_time   DATETIME     NULL,
    UNIQUE KEY uk_tnum (num),
    KEY idx_num (num)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='教师表';

-- ==================== classes ====================
CREATE TABLE IF NOT EXISTS classes (
    id               INT AUTO_INCREMENT PRIMARY KEY,
    num              VARCHAR(30)  NOT NULL COMMENT '班级编号',
    name             VARCHAR(30)  NOT NULL COMMENT '班级名称',
    class_start_time DATETIME     NULL     COMMENT '开课时间',
    head_teacher_id  INT          NULL     COMMENT '班主任ID',
    coach_teacher_id INT          NULL     COMMENT '授课老师ID',
    tutor_teacher_id INT          NULL     COMMENT '助教老师ID',
    create_time      DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP,
    update_time      DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    is_deleted       TINYINT(1)   NOT NULL DEFAULT 0,
    delete_time      DATETIME     NULL,
    UNIQUE KEY uk_class_num (num),
    KEY idx_head_teacher (head_teacher_id),
    KEY idx_coach_teacher (coach_teacher_id),
    KEY idx_tutor_teacher (tutor_teacher_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='班级表';

ALTER TABLE classes
    ADD CONSTRAINT fk_classes_head_teacher  FOREIGN KEY (head_teacher_id)  REFERENCES teachers(id) ON DELETE SET NULL ON UPDATE CASCADE,
    ADD CONSTRAINT fk_classes_coach_teacher FOREIGN KEY (coach_teacher_id) REFERENCES teachers(id) ON DELETE SET NULL ON UPDATE CASCADE,
    ADD CONSTRAINT fk_classes_tutor_teacher FOREIGN KEY (tutor_teacher_id) REFERENCES teachers(id) ON DELETE SET NULL ON UPDATE CASCADE;

-- ==================== students ====================
CREATE TABLE IF NOT EXISTS students (
    id              INT AUTO_INCREMENT PRIMARY KEY,
    num             VARCHAR(30)  NOT NULL COMMENT '学生编号',
    name            VARCHAR(30)  NOT NULL DEFAULT '' COMMENT '姓名',
    age             INT          NOT NULL DEFAULT 18 COMMENT '年龄',
    sex             INT          NOT NULL DEFAULT 0  COMMENT '性别：0未知 1男 2女',
    home_place      VARCHAR(50)  NULL     COMMENT '家乡',
    college         VARCHAR(50)  NULL     COMMENT '毕业院校',
    specialty       VARCHAR(50)  NULL     COMMENT '专业',
    enrollment_time DATETIME     NULL     COMMENT '入学时间',
    graduate_time   DATETIME     NULL     COMMENT '毕业时间',
    education       VARCHAR(50)  NULL     COMMENT '学历',
    class_id        INT          NOT NULL DEFAULT 0  COMMENT '所属班级ID',
    advisor_id      INT          NULL     COMMENT '顾问老师ID',
    create_time     DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP,
    update_time     DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    is_deleted      TINYINT(1)   NOT NULL DEFAULT 0,
    delete_time     DATETIME     NULL,
    UNIQUE KEY uk_snum (num),
    KEY idx_class_id (class_id),
    KEY idx_advisor_id (advisor_id),
    KEY idx_class_deleted (class_id, is_deleted)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='学生表';

ALTER TABLE students
    ADD CONSTRAINT fk_students_class   FOREIGN KEY (class_id)   REFERENCES classes(id)  ON DELETE RESTRICT  ON UPDATE CASCADE,
    ADD CONSTRAINT fk_students_advisor FOREIGN KEY (advisor_id) REFERENCES teachers(id) ON DELETE SET NULL ON UPDATE CASCADE;

-- ==================== scores ====================
CREATE TABLE IF NOT EXISTS scores (
    id          INT AUTO_INCREMENT PRIMARY KEY,
    sid         INT          NOT NULL COMMENT '学生ID',
    num         VARCHAR(30)  NOT NULL COMMENT '考核序次',
    score       DECIMAL(10,2) NOT NULL COMMENT '分数',
    create_time DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP,
    update_time DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    is_deleted  TINYINT(1)   NOT NULL DEFAULT 0,
    delete_time DATETIME     NULL,
    UNIQUE KEY uk_sid_score (sid, num),
    KEY idx_sid (sid)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='成绩表';

ALTER TABLE scores
    ADD CONSTRAINT fk_scores_student FOREIGN KEY (sid) REFERENCES students(id) ON DELETE CASCADE ON UPDATE CASCADE;

-- ==================== employment ====================
CREATE TABLE IF NOT EXISTS employment (
    id                   INT AUTO_INCREMENT PRIMARY KEY,
    sid                  INT          NOT NULL COMMENT '学生ID',
    class_id             INT          NOT NULL COMMENT '班级ID',
    employment_open_time  DATETIME     NULL     COMMENT '就业开放时间',
    offer_recived_time    DATETIME     NULL     COMMENT 'Offer下发时间',
    employment_company    VARCHAR(50)  NULL     COMMENT '就业公司',
    employment_salary     DECIMAL(20,5) NULL    COMMENT '就业薪资（月薪）',
    create_time          DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP,
    update_time          DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    is_deleted           TINYINT(1)   NOT NULL DEFAULT 0,
    delete_time          DATETIME     NULL,
    UNIQUE KEY uk_sid (sid),
    KEY idx_class_id (class_id),
    KEY idx_class_deleted (class_id, is_deleted)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='就业表';

ALTER TABLE employment
    ADD CONSTRAINT fk_employment_student FOREIGN KEY (sid)     REFERENCES students(id) ON DELETE CASCADE ON UPDATE CASCADE,
    ADD CONSTRAINT fk_employment_class   FOREIGN KEY (class_id) REFERENCES classes(id)  ON DELETE RESTRICT  ON UPDATE CASCADE;
```

---

## 5. 索引设计说明

| 表 | 索引名 | 类型 | 字段 | 优化场景 |
|----|--------|------|------|----------|
| students | uk_snum | 唯一 | num | 按学号精确查询 |
| students | idx_class_id | 普通 | class_id | 按班级查学生列表 |
| students | idx_advisor_id | 普通 | advisor_id | 按顾问查学生 |
| students | idx_class_deleted | 联合 | (class_id, is_deleted) | 查某班未删除学生（覆盖常见过滤） |
| classes | uk_class_num | 唯一 | num | 按班级编号精确查询 |
| classes | idx_head_teacher | 普通 | head_teacher_id | 按班主任查班级 |
| scores | uk_sid_score | 唯一 | (sid, num) | 防止重复录入，加速组合查询 |
| scores | idx_sid | 普通 | sid | 按学生查成绩 |
| employment | uk_sid | 唯一 | sid | 保证一人一条就业记录 |
| employment | idx_class_id | 普通 | class_id | 按班级统计就业 |
| employment | idx_class_deleted | 联合 | (class_id, is_deleted) | 班级就业统计过滤已删除记录 |

---

## 6. 数据字典表（V2.0 规划）

```sql
CREATE TABLE IF NOT EXISTS dict_items (
    id          INT AUTO_INCREMENT PRIMARY KEY,
    dict_type   VARCHAR(50)  NOT NULL COMMENT '字典类型：sex, education, college, specialty, coach_area',
    dict_code   VARCHAR(50)  NOT NULL COMMENT '字典编码，业务表存储的值',
    dict_label  VARCHAR(100) NOT NULL COMMENT '显示名称',
    sort_order  INT          NOT NULL DEFAULT 0 COMMENT '排序权重',
    is_enabled  TINYINT(1)   NOT NULL DEFAULT 1 COMMENT '是否启用',
    create_time DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP,
    update_time DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    is_deleted  TINYINT(1)   NOT NULL DEFAULT 0,
    delete_time DATETIME     NULL,
    UNIQUE KEY uk_type_code (dict_type, dict_code),
    KEY idx_type (dict_type)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='通用字典表';

-- 初始数据
INSERT INTO dict_items (dict_type, dict_code, dict_label, sort_order) VALUES
('sex',      '0', '未知', 1),
('sex',      '1', '男',   2),
('sex',      '2', '女',   3),
('education','bachelor', '本科', 1),
('education','master',   '硕士', 2),
('education','phd',      '博士', 3),
('coach_area','app',     '应用', 1),
('coach_area','project', '项目', 2),
('coach_area','algorithm','算法', 3);
```

**引用方式（应用层 JOIN）：**
```sql
-- 查询学生时关联字典获取可读名称
SELECT s.*,
       d_sex.dict_label AS sex_label,
       d_edu.dict_label AS education_label
FROM students s
LEFT JOIN dict_items d_sex ON d_sex.dict_type='sex' AND d_sex.dict_code=CAST(s.sex AS CHAR)
LEFT JOIN dict_items d_edu ON d_edu.dict_type='education' AND d_edu.dict_code=s.education
WHERE s.is_deleted=0;
```

---

## 7. 历史数据归档策略（V3.0 规划）

当数据量达到千万级时，考虑以下归档方案：

| 策略 | 适用场景 | 说明 |
|------|----------|------|
| 分区表（PARTITION BY RANGE） | 按年份归档 | 对 `create_time` 做范围分区，老分区可迁移至冷存储 |
| 归档表（_history 后缀） | 毕业生数据 | 将已毕业学生的成绩/就业记录移入 `students_history` 等归档表 |
| 分库分表 | 超大规模 | 按 `class_id` 哈希分片，需引入 ShardingSphere 或应用层分片 |

**归档判断条件：**
- 学生 `graduate_time` 距今超过 2 年
- 或主动标记为"已归档"状态