Oracle数据库表的约束主键/外键/唯一/非空约束的创建与实战详解

-- 查看当前用户下所有约束
SELECT constraint_name, constraint_type, table_name, status, validated
FROM user_constraints
WHERE table_name IN ('EMPLOYEES', 'DEPARTMENTS');

-- 1️⃣ 创建 DEPARTMENTS 表（主键 + 非空）
CREATE TABLE departments (
    dept_id     NUMBER(6),
    dept_name   VARCHAR2(50),
    location    VARCHAR2(20),
    created_at  DATE DEFAULT SYSDATE,
    CONSTRAINT pk_departments PRIMARY KEY (dept_id),
    CONSTRAINT chk_dept_name_not_empty CHECK (TRIM(dept_name) IS NOT NULL),
    CONSTRAINT chk_location_uppercase CHECK (location = UPPER(location))
);

-- 2️⃣ 创建 EMPLOYEES 表（主键 + 外键 + 唯一 + 非空 + 检查）
CREATE TABLE employees (
    emp_id      NUMBER(8),
    full_name   VARCHAR2(100),
    email       VARCHAR2(100),
    salary      NUMBER(10,2),
    dept_id     NUMBER(6),
    hire_date   DATE,
    manager_id  NUMBER(8), -- 自关联外键（可为空）
    CONSTRAINT pk_employees PRIMARY KEY (emp_id),
    CONSTRAINT uk_employee_email UNIQUE (email),
    CONSTRAINT fk_employees_dept FOREIGN KEY (dept_id) REFERENCES departments(dept_id),
    CONSTRAINT fk_employees_manager FOREIGN KEY (manager_id) REFERENCES employees(emp_id),
    CONSTRAINT nn_employee_name CHECK (full_name IS NOT NULL),
    CONSTRAINT nn_employee_hiredate CHECK (hire_date IS NOT NULL),
    CONSTRAINT chk_salary_positive CHECK (salary > 0),
    CONSTRAINT chk_email_format CHECK (REGEXP_LIKE(email, '^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$'))
);

-- 3️⃣ 为外键列添加索引（关键性能优化！）
CREATE INDEX idx_emp_dept_id ON employees(dept_id);
CREATE INDEX idx_emp_manager_id ON employees(manager_id);

INSERT INTO employees (emp_id, full_name) VALUES (1, 'Alice'); -- OK
INSERT INTO employees (emp_id, full_name) VALUES (1, 'Bob');   -- ORA-00001!
INSERT INTO employees (emp_id, full_name) VALUES (NULL, 'Charlie'); -- ORA-01400!

-- 更安全的外键定义（明确拒绝级联删除）
ALTER TABLE employees 
ADD CONSTRAINT fk_employees_dept_safe 
FOREIGN KEY (dept_id) REFERENCES departments(dept_id) 
ON DELETE RESTRICT; -- Oracle 12c+ 支持（等价于默认 NO ACTION，但语义更清晰）

-- ✅ 正确：为外键列创建索引（大幅提升 DELETE/UPDATE 性能）
CREATE INDEX idx_emp_dept_fk ON employees(dept_id);

-- ❌ 危险：无索引外键导致全表扫描
-- DELETE FROM departments WHERE dept_id = 10; -- 可能锁表数分钟！

-- 创建测试表
CREATE TABLE test_unique (
    id NUMBER,
    code VARCHAR2(10),
    CONSTRAINT uk_test_code UNIQUE (code)
);

-- 插入数据（全部成功！）
INSERT INTO test_unique VALUES (1, 'A');    -- OK
INSERT INTO test_unique VALUES (2, 'B');    -- OK
INSERT INTO test_unique VALUES (3, NULL);  -- OK ← 允许
INSERT INTO test_unique VALUES (4, NULL);  -- OK ← 允许第二个 NULL
INSERT INTO test_unique VALUES (5, 'A');    -- ORA-00001! ← 重复 'A'

SELECT * FROM test_unique;
-- 结果：
-- ID | CODE
-- 1  | A
-- 2  | B
-- 3  | (null)
-- 4  | (null)

-- 方式1：列定义时声明（最常见）
CREATE TABLE products (
    prod_id NUMBER NOT NULL,
    name VARCHAR2(100) NOT NULL
);

-- 方式2：表级约束（可命名，便于管理）
CREATE TABLE products2 (
    prod_id NUMBER,
    name VARCHAR2(100),
    CONSTRAINT nn_products_name CHECK (name IS NOT NULL)
);

-- 方式3：ALTER TABLE 添加（适用于已有表）
ALTER TABLE products ADD CONSTRAINT nn_products_id CHECK (prod_id IS NOT NULL);

-- ❌ 错误认知：DEFAULT 可替代 NOT NULL
CREATE TABLE t1 (col VARCHAR2(10) DEFAULT 'N/A'); -- col 仍可 INSERT NULL！

-- ✅ 正确组合：DEFAULT + NOT NULL = 真正的“必填且有默认”
CREATE TABLE t2 (col VARCHAR2(10) DEFAULT 'N/A' NOT NULL);
INSERT INTO t2 VALUES (DEFAULT); -- 插入 'N/A'
INSERT INTO t2 VALUES (NULL);     -- ORA-01400!

-- Step 1: 禁用外键（避免迁移中断）
ALTER TABLE employees DISABLE CONSTRAINT fk_employees_dept;

-- Step 2: 批量插入（含脏数据）
INSERT /*+ APPEND */ INTO employees SELECT * FROM legacy_employees;

-- Step 3: 修复脏数据（如 dept_id=0 → 设为 NULL 或映射到默认部门）
UPDATE employees SET dept_id = NULL WHERE dept_id NOT IN (SELECT dept_id FROM departments);

-- Step 4: 启用约束，但跳过历史数据验证（高效！）
ALTER TABLE employees ENABLE NOVALIDATE CONSTRAINT fk_employees_dept;

-- Step 5: 后续新插入数据将严格受检，确保增量质量
INSERT INTO employees VALUES (999, 'New Guy', 'new@company.com', 8000, 9999); -- ORA-02291!

@Service
public class EmployeeService {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    public void createEmployee(Employee employee) {
        String sql = "INSERT INTO employees (emp_id, full_name, email, salary, dept_id, hire_date) " +
                     "VALUES (?, ?, ?, ?, ?, ?)";
        
        try {
            jdbcTemplate.update(sql,
                employee.getEmpId(),
                employee.getFullName(),
                employee.getEmail(),
                employee.getSalary(),
                employee.getDeptId(),
                employee.getHireDate()
            );
        } catch (DataIntegrityViolationException e) {
            SQLException sqlEx = getRootCause(e, SQLException.class);
            if (sqlEx != null) {
                int errorCode = sqlEx.getErrorCode();
                String sqlState = sqlEx.getSQLState();

                // Oracle 特定错误码映射（权威来源见下方链接）
                if (errorCode == 1) { // ORA-00001: unique constraint violated
                    throw new BusinessException("邮箱 " + employee.getEmail() + " 已被注册，请更换");
                } else if (errorCode == 1400) { // ORA-01400: cannot insert NULL into
                    throw new BusinessException("必填字段缺失，请检查表单");
                } else if (errorCode == 2291) { // ORA-02291: integrity constraint violated - parent key not found
                    throw new BusinessException("所属部门不存在，请联系管理员");
                } else if (errorCode == 2290) { // ORA-02290: check constraint violated
                    throw new BusinessException("薪资必须大于0，请输入有效数字");
                }
            }
            throw e; // 其他异常透传
        }
    }

    @SuppressWarnings("unchecked")
    private <T extends Throwable> T getRootCause(Throwable t, Class<T> type) {
        Throwable cause = t;
        while (cause != null) {
            if (type.isInstance(cause)) {
                return (T) cause;
            }
            cause = cause.getCause();
        }
        return null;
    }
}

@Entity
@Table(name = "employees",
    uniqueConstraints = {
        @UniqueConstraint(columnNames = "email", name = "uk_employee_email")
    },
    indexes = {
        @Index(columnList = "dept_id", name = "idx_emp_dept_id")
    }
)
public class Employee {

    @Id
    @Column(name = "emp_id", nullable = false, precision = 8)
    private Long empId;

    @Column(name = "full_name", nullable = false, length = 100)
    private String fullName;

    @Column(name = "email", nullable = false, length = 100, unique = true)
    private String email;

    @Column(name = "salary", nullable = false, precision = 10, scale = 2)
    private BigDecimal salary;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(
        name = "dept_id",
        referencedColumnName = "dept_id",
        foreignKey = @ForeignKey(name = "fk_employees_dept") // 显式命名外键
    )
    private Department department;

    @Column(name = "hire_date", nullable = false)
    @Temporal(TemporalType.DATE)
    private Date hireDate;

    // getters & setters ...
}

spring:
  jpa:
    hibernate:
      ddl-auto: validate # 生产环境强烈推荐！校验实体与DB结构是否一致，不修改
      # ddl-auto: none # 更安全：完全禁用自动DDL，由Flyway/Liquibase管理
    show-sql: true
    properties:
      hibernate:
        format_sql: true

@RestControllerAdvice
public class ConstraintExceptionHandler {

    private static final Map<Integer, String> ORACLE_ERROR_MESSAGES = Map.of(
        1, "数据已存在，请勿重复操作",
        1400, "缺少必要信息，请完善表单",
        2291, "关联数据不存在，请确认输入正确",
        2290, "输入内容不符合规则，请按提示修改",
        2292, "该数据被其他记录引用，无法删除"
    );

    @ExceptionHandler(DataIntegrityViolationException.class)
    public ResponseEntity<ApiResponse<String>> handleConstraintViolation(
            DataIntegrityViolationException ex) {

        SQLException sqlEx = getRootCause(ex, SQLException.class);
        if (sqlEx != null) {
            Integer errorCode = sqlEx.getErrorCode();
            String message = ORACLE_ERROR_MESSAGES.getOrDefault(
                errorCode, "系统繁忙，请稍后重试"
            );
            return ResponseEntity.badRequest()
                .body(ApiResponse.error(message));
        }

        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
            .body(ApiResponse.error("未知错误"));
    }

    @SuppressWarnings("unchecked")
    private <T extends Throwable> T getRootCause(Throwable t, Class<T> type) {
        Throwable cause = t;
        while (cause != null) {
            if (type.isInstance(cause)) {
                return (T) cause;
            }
            cause = cause.getCause();
        }
        return null;
    }
}

-- 问题：部门需指定经理（员工），员工又需指定部门 → 循环依赖！
CREATE TABLE departments (
    dept_id NUMBER PRIMARY KEY,
    dept_name VARCHAR2(50),
    manager_id NUMBER,
    CONSTRAINT fk_dept_manager FOREIGN KEY (manager_id) REFERENCES employees(emp_id)
);

CREATE TABLE employees (
    emp_id NUMBER PRIMARY KEY,
    name VARCHAR2(100),
    dept_id NUMBER,
    CONSTRAINT fk_emp_dept FOREIGN KEY (dept_id) REFERENCES departments(dept_id)
);

-- 修改外键为可延迟
ALTER TABLE departments 
MODIFY CONSTRAINT fk_dept_manager 
DEFERRABLE INITIALLY DEFERRED;

-- 现在可以这样操作（事务内）：
BEGIN
    INSERT INTO employees VALUES (1, 'Alice', NULL); -- 先插员工（dept_id 为 NULL）
    INSERT INTO departments VALUES (10, 'IT', 1);     -- 再插部门（引用员工1）
    INSERT INTO employees VALUES (2, 'Bob', 10);      -- 最后设置 Bob 的部门
    COMMIT; -- 提交时统一验证所有延迟约束
EXCEPTION
    WHEN OTHERS THEN
        ROLLBACK;
        RAISE;
END;

-- 一个员工在同一个部门内只能有一个职位
CREATE TABLE employee_positions (
    emp_id NUMBER,
    dept_id NUMBER,
    position VARCHAR2(50),
    start_date DATE,
    end_date DATE,
    CONSTRAINT pk_emp_pos PRIMARY KEY (emp_id, dept_id, start_date),
    CONSTRAINT uk_emp_dept_pos UNIQUE (emp_id, dept_id, position) -- 同人同部门不能重复职位
);

-- 或更实用的：防止同一时间段内重复排班
ALTER TABLE employee_positions 
ADD CONSTRAINT uk_emp_dept_date 
UNIQUE (emp_id, dept_id, 
    TRUNC(start_date), 
    TRUNC(end_date)
);

-- 定义邮箱域名虚拟列，并强制只允许公司域名
CREATE TABLE users (
    user_id NUMBER PRIMARY KEY,
    email VARCHAR2(100),
    domain AS (SUBSTR(email, INSTR(email, '@') + 1)) VIRTUAL,
    CONSTRAINT chk_email_domain CHECK (domain IN ('company.com', 'subsidiary.com'))
);

-- 插入测试
INSERT INTO users (user_id, email) VALUES (1, 'alice@company.com'); -- OK
INSERT INTO users (user_id, email) VALUES (2, 'bob@gmail.com');     -- ORA-02290!