procedures functions

文件信息

📄 原文件：05_procedures_functions.sql
🔤 语言：SQL

SQL 脚本

sql

-- ============================================================
--                    MySQL 存储过程与函数
-- ============================================================
-- 本文件介绍 MySQL 存储过程、函数和触发器。
-- ============================================================

USE learn_mysql;

-- ============================================================
--                    1. 存储过程基础
-- ============================================================

/*
存储过程优点：
- 减少网络传输
- 提高性能（预编译）
- 代码复用
- 安全性（限制直接访问表）

存储过程 vs 函数：
- 存储过程：可有多个输出，可执行 DML/DDL，CALL 调用
- 函数：只能返回一个值，可在 SQL 中使用
*/

-- 更改语句结束符（存储过程内部使用分号）
DELIMITER //

-- --- 基本存储过程 ---

-- 无参数存储过程
CREATE PROCEDURE get_all_employees()
BEGIN
    SELECT * FROM employees;
END//

-- 调用存储过程
DELIMITER ;
CALL get_all_employees();

-- --- 带参数的存储过程 ---

DELIMITER //

-- IN 参数（输入）
CREATE PROCEDURE get_employee_by_id(
    IN emp_id INT
)
BEGIN
    SELECT * FROM employees WHERE id = emp_id;
END//

-- OUT 参数（输出）
CREATE PROCEDURE get_employee_count(
    OUT total INT
)
BEGIN
    SELECT COUNT(*) INTO total FROM employees;
END//

-- INOUT 参数（输入输出）
CREATE PROCEDURE increase_salary(
    INOUT salary DECIMAL(10, 2),
    IN percentage DECIMAL(5, 2)
)
BEGIN
    SET salary = salary * (1 + percentage / 100);
END//

DELIMITER ;

-- 调用示例
CALL get_employee_by_id(1);

CALL get_employee_count(@count);
SELECT @count AS employee_count;

SET @sal = 10000;
CALL increase_salary(@sal, 10);
SELECT @sal AS new_salary;  -- 11000


-- ============================================================
--                    2. 变量与流程控制
-- ============================================================

DELIMITER //

-- --- 变量声明和赋值 ---
CREATE PROCEDURE variable_demo()
BEGIN
    -- 声明变量
    DECLARE emp_name VARCHAR(50);
    DECLARE emp_salary DECIMAL(10, 2) DEFAULT 0;
    DECLARE total_count INT;

    -- 赋值方式1：SET
    SET emp_name = 'Test';
    SET emp_salary = 5000;

    -- 赋值方式2：SELECT INTO
    SELECT COUNT(*) INTO total_count FROM employees;

    -- 赋值方式3：SELECT INTO 多个变量
    SELECT name, salary INTO emp_name, emp_salary
    FROM employees WHERE id = 1;

    -- 输出结果
    SELECT emp_name, emp_salary, total_count;
END//

-- --- IF 条件 ---
CREATE PROCEDURE check_salary_level(
    IN emp_id INT,
    OUT level VARCHAR(20)
)
BEGIN
    DECLARE emp_salary DECIMAL(10, 2);

    SELECT salary INTO emp_salary
    FROM employees WHERE id = emp_id;

    IF emp_salary >= 25000 THEN
        SET level = '高级';
    ELSEIF emp_salary >= 15000 THEN
        SET level = '中级';
    ELSE
        SET level = '初级';
    END IF;
END//

-- --- CASE 语句 ---
CREATE PROCEDURE get_department_info(
    IN dept_id INT,
    OUT dept_type VARCHAR(20)
)
BEGIN
    DECLARE dept_name VARCHAR(50);

    SELECT name INTO dept_name
    FROM departments WHERE id = dept_id;

    CASE dept_name
        WHEN '技术部' THEN SET dept_type = '研发';
        WHEN '市场部' THEN SET dept_type = '销售';
        WHEN '财务部' THEN SET dept_type = '管理';
        WHEN '人事部' THEN SET dept_type = '管理';
        ELSE SET dept_type = '其他';
    END CASE;
END//

-- --- CASE 搜索形式 ---
CREATE PROCEDURE evaluate_performance(
    IN emp_id INT,
    OUT evaluation VARCHAR(20)
)
BEGIN
    DECLARE emp_salary DECIMAL(10, 2);
    DECLARE hire_years INT;

    SELECT salary,
           TIMESTAMPDIFF(YEAR, hire_date, CURDATE())
    INTO emp_salary, hire_years
    FROM employees WHERE id = emp_id;

    CASE
        WHEN emp_salary > 20000 AND hire_years > 3 THEN
            SET evaluation = '优秀';
        WHEN emp_salary > 15000 OR hire_years > 2 THEN
            SET evaluation = '良好';
        ELSE
            SET evaluation = '待提升';
    END CASE;
END//

DELIMITER ;

-- 测试
CALL variable_demo();

CALL check_salary_level(1, @level);
SELECT @level;

CALL evaluate_performance(1, @eval);
SELECT @eval;


-- ============================================================
--                    3. 循环结构
-- ============================================================

DELIMITER //

-- --- WHILE 循环 ---
CREATE PROCEDURE while_demo()
BEGIN
    DECLARE i INT DEFAULT 1;
    DECLARE result VARCHAR(100) DEFAULT '';

    WHILE i <= 5 DO
        SET result = CONCAT(result, i, ' ');
        SET i = i + 1;
    END WHILE;

    SELECT result AS numbers;
END//

-- --- REPEAT 循环（类似 do-while）---
CREATE PROCEDURE repeat_demo()
BEGIN
    DECLARE i INT DEFAULT 1;
    DECLARE total INT DEFAULT 0;

    REPEAT
        SET total = total + i;
        SET i = i + 1;
    UNTIL i > 10
    END REPEAT;

    SELECT total AS sum_1_to_10;  -- 55
END//

-- --- LOOP 循环（无限循环，需要 LEAVE 退出）---
CREATE PROCEDURE loop_demo()
BEGIN
    DECLARE i INT DEFAULT 0;

    loop_label: LOOP
        SET i = i + 1;

        -- 跳过偶数
        IF i MOD 2 = 0 THEN
            ITERATE loop_label;  -- 类似 continue
        END IF;

        -- 大于 10 退出
        IF i > 10 THEN
            LEAVE loop_label;  -- 类似 break
        END IF;

        SELECT i AS odd_number;
    END LOOP loop_label;
END//

-- --- 实际应用：批量更新 ---
CREATE PROCEDURE batch_update_salary(
    IN percentage DECIMAL(5, 2),
    IN batch_size INT
)
BEGIN
    DECLARE done INT DEFAULT 0;
    DECLARE total_updated INT DEFAULT 0;
    DECLARE rows_affected INT;

    batch_loop: LOOP
        UPDATE employees
        SET salary = salary * (1 + percentage / 100)
        WHERE salary < 20000
        LIMIT batch_size;

        SET rows_affected = ROW_COUNT();
        SET total_updated = total_updated + rows_affected;

        IF rows_affected = 0 THEN
            LEAVE batch_loop;
        END IF;

        -- 可以在这里添加延迟或事务控制
        COMMIT;
    END LOOP;

    SELECT total_updated AS employees_updated;
END//

DELIMITER ;

-- 测试
CALL while_demo();
CALL repeat_demo();


-- ============================================================
--                    4. 游标（Cursor）
-- ============================================================

DELIMITER //

-- 基本游标使用
CREATE PROCEDURE cursor_demo()
BEGIN
    -- 声明变量
    DECLARE done INT DEFAULT 0;
    DECLARE emp_id INT;
    DECLARE emp_name VARCHAR(50);
    DECLARE emp_salary DECIMAL(10, 2);

    -- 声明游标
    DECLARE emp_cursor CURSOR FOR
        SELECT id, name, salary FROM employees WHERE department_id = 1;

    -- 声明处理器（当游标到达末尾时设置 done = 1）
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

    -- 创建临时表存储结果
    CREATE TEMPORARY TABLE IF NOT EXISTS cursor_results (
        id INT,
        name VARCHAR(50),
        salary DECIMAL(10, 2),
        bonus DECIMAL(10, 2)
    );

    TRUNCATE TABLE cursor_results;

    -- 打开游标
    OPEN emp_cursor;

    -- 循环读取
    read_loop: LOOP
        FETCH emp_cursor INTO emp_id, emp_name, emp_salary;

        IF done THEN
            LEAVE read_loop;
        END IF;

        -- 处理每一行
        INSERT INTO cursor_results VALUES (
            emp_id,
            emp_name,
            emp_salary,
            emp_salary * 0.1  -- 10% 奖金
        );
    END LOOP;

    -- 关闭游标
    CLOSE emp_cursor;

    -- 返回结果
    SELECT * FROM cursor_results;
END//

-- 复杂游标示例：生成报表
CREATE PROCEDURE generate_dept_report()
BEGIN
    DECLARE done INT DEFAULT 0;
    DECLARE dept_id INT;
    DECLARE dept_name VARCHAR(50);

    DECLARE dept_cursor CURSOR FOR
        SELECT id, name FROM departments;

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

    -- 创建报表临时表
    DROP TEMPORARY TABLE IF EXISTS dept_report;
    CREATE TEMPORARY TABLE dept_report (
        department VARCHAR(50),
        employee_count INT,
        total_salary DECIMAL(12, 2),
        avg_salary DECIMAL(10, 2),
        max_salary DECIMAL(10, 2),
        min_salary DECIMAL(10, 2)
    );

    OPEN dept_cursor;

    dept_loop: LOOP
        FETCH dept_cursor INTO dept_id, dept_name;

        IF done THEN
            LEAVE dept_loop;
        END IF;

        INSERT INTO dept_report
        SELECT
            dept_name,
            COUNT(*),
            SUM(salary),
            AVG(salary),
            MAX(salary),
            MIN(salary)
        FROM employees
        WHERE department_id = dept_id;
    END LOOP;

    CLOSE dept_cursor;

    SELECT * FROM dept_report;
END//

DELIMITER ;

-- 测试游标
CALL cursor_demo();
CALL generate_dept_report();


-- ============================================================
--                    5. 自定义函数
-- ============================================================

DELIMITER //

-- 标量函数
CREATE FUNCTION get_full_name(
    first_name VARCHAR(50),
    last_name VARCHAR(50)
)
RETURNS VARCHAR(100)
DETERMINISTIC  -- 相同输入总是返回相同结果
BEGIN
    RETURN CONCAT(first_name, ' ', last_name);
END//

-- 计算函数
CREATE FUNCTION calculate_tax(
    salary DECIMAL(10, 2)
)
RETURNS DECIMAL(10, 2)
DETERMINISTIC
BEGIN
    DECLARE tax DECIMAL(10, 2);

    IF salary <= 5000 THEN
        SET tax = 0;
    ELSEIF salary <= 10000 THEN
        SET tax = (salary - 5000) * 0.1;
    ELSEIF salary <= 20000 THEN
        SET tax = 500 + (salary - 10000) * 0.2;
    ELSE
        SET tax = 2500 + (salary - 20000) * 0.3;
    END IF;

    RETURN tax;
END//

-- 查询相关函数
CREATE FUNCTION get_department_name(
    dept_id INT
)
RETURNS VARCHAR(50)
READS SQL DATA  -- 函数读取数据但不修改
BEGIN
    DECLARE dept_name VARCHAR(50);

    SELECT name INTO dept_name
    FROM departments
    WHERE id = dept_id;

    RETURN COALESCE(dept_name, '未分配');
END//

-- 业务逻辑函数
CREATE FUNCTION get_employee_level(
    emp_id INT
)
RETURNS VARCHAR(20)
READS SQL DATA
BEGIN
    DECLARE emp_salary DECIMAL(10, 2);
    DECLARE hire_years INT;

    SELECT salary, TIMESTAMPDIFF(YEAR, hire_date, CURDATE())
    INTO emp_salary, hire_years
    FROM employees WHERE id = emp_id;

    IF emp_salary IS NULL THEN
        RETURN '未知';
    END IF;

    IF emp_salary >= 25000 AND hire_years >= 5 THEN
        RETURN '资深专家';
    ELSEIF emp_salary >= 20000 AND hire_years >= 3 THEN
        RETURN '高级';
    ELSEIF emp_salary >= 15000 THEN
        RETURN '中级';
    ELSE
        RETURN '初级';
    END IF;
END//

DELIMITER ;

-- 使用函数
SELECT get_full_name('John', 'Doe') AS full_name;

SELECT
    name,
    salary,
    calculate_tax(salary) AS tax,
    salary - calculate_tax(salary) AS net_salary
FROM employees;

SELECT
    name,
    get_department_name(department_id) AS department,
    get_employee_level(id) AS level
FROM employees;


-- ============================================================
--                    6. 触发器
-- ============================================================

-- 创建日志表
CREATE TABLE IF NOT EXISTS employee_audit (
    id INT AUTO_INCREMENT PRIMARY KEY,
    employee_id INT,
    action VARCHAR(10),
    old_data JSON,
    new_data JSON,
    changed_by VARCHAR(50),
    changed_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

DELIMITER //

-- BEFORE INSERT 触发器
CREATE TRIGGER trg_employee_before_insert
BEFORE INSERT ON employees
FOR EACH ROW
BEGIN
    -- 自动设置创建时间
    IF NEW.created_at IS NULL THEN
        SET NEW.created_at = NOW();
    END IF;

    -- 数据验证
    IF NEW.salary < 0 THEN
        SIGNAL SQLSTATE '45000'
        SET MESSAGE_TEXT = '薪资不能为负数';
    END IF;
END//

-- AFTER INSERT 触发器
CREATE TRIGGER trg_employee_after_insert
AFTER INSERT ON employees
FOR EACH ROW
BEGIN
    INSERT INTO employee_audit (employee_id, action, new_data, changed_by)
    VALUES (
        NEW.id,
        'INSERT',
        JSON_OBJECT('name', NEW.name, 'salary', NEW.salary),
        CURRENT_USER()
    );
END//

-- BEFORE UPDATE 触发器
CREATE TRIGGER trg_employee_before_update
BEFORE UPDATE ON employees
FOR EACH ROW
BEGIN
    -- 限制薪资涨幅不超过 50%
    IF NEW.salary > OLD.salary * 1.5 THEN
        SIGNAL SQLSTATE '45000'
        SET MESSAGE_TEXT = '薪资涨幅不能超过50%';
    END IF;
END//

-- AFTER UPDATE 触发器
CREATE TRIGGER trg_employee_after_update
AFTER UPDATE ON employees
FOR EACH ROW
BEGIN
    INSERT INTO employee_audit (employee_id, action, old_data, new_data, changed_by)
    VALUES (
        NEW.id,
        'UPDATE',
        JSON_OBJECT('name', OLD.name, 'salary', OLD.salary),
        JSON_OBJECT('name', NEW.name, 'salary', NEW.salary),
        CURRENT_USER()
    );
END//

-- AFTER DELETE 触发器
CREATE TRIGGER trg_employee_after_delete
AFTER DELETE ON employees
FOR EACH ROW
BEGIN
    INSERT INTO employee_audit (employee_id, action, old_data, changed_by)
    VALUES (
        OLD.id,
        'DELETE',
        JSON_OBJECT('name', OLD.name, 'salary', OLD.salary),
        CURRENT_USER()
    );
END//

DELIMITER ;

-- 查看触发器
SHOW TRIGGERS;

SELECT * FROM information_schema.TRIGGERS
WHERE TRIGGER_SCHEMA = 'learn_mysql';


-- ============================================================
--                    7. 错误处理
-- ============================================================

DELIMITER //

CREATE PROCEDURE error_handling_demo()
BEGIN
    -- 声明变量
    DECLARE error_occurred BOOLEAN DEFAULT FALSE;
    DECLARE error_message VARCHAR(255);

    -- 声明错误处理器
    DECLARE EXIT HANDLER FOR SQLEXCEPTION
    BEGIN
        GET DIAGNOSTICS CONDITION 1
            error_message = MESSAGE_TEXT;
        SET error_occurred = TRUE;
        ROLLBACK;
        SELECT CONCAT('错误: ', error_message) AS error;
    END;

    -- 特定错误处理
    DECLARE CONTINUE HANDLER FOR 1062  -- 重复键错误
    BEGIN
        SET error_message = '记录已存在';
    END;

    START TRANSACTION;

    -- 尝试插入数据
    INSERT INTO employees (name, email, salary, hire_date)
    VALUES ('Test', 'test@test.com', 10000, CURDATE());

    IF error_occurred THEN
        SELECT '操作失败' AS result;
    ELSE
        COMMIT;
        SELECT '操作成功' AS result;
    END IF;
END//

-- 使用 SIGNAL 抛出自定义错误
CREATE PROCEDURE validate_and_insert(
    IN emp_name VARCHAR(50),
    IN emp_salary DECIMAL(10, 2)
)
BEGIN
    IF emp_name IS NULL OR emp_name = '' THEN
        SIGNAL SQLSTATE '45000'
        SET MESSAGE_TEXT = '员工姓名不能为空';
    END IF;

    IF emp_salary < 0 THEN
        SIGNAL SQLSTATE '45000'
        SET MESSAGE_TEXT = '薪资不能为负数',
        MYSQL_ERRNO = 1644;
    END IF;

    INSERT INTO employees (name, email, salary, hire_date)
    VALUES (emp_name, CONCAT(emp_name, '@company.com'), emp_salary, CURDATE());

    SELECT '插入成功' AS result;
END//

DELIMITER ;


-- ============================================================
--                    8. 管理存储过程和函数
-- ============================================================

-- 查看存储过程
SHOW PROCEDURE STATUS WHERE Db = 'learn_mysql';

-- 查看函数
SHOW FUNCTION STATUS WHERE Db = 'learn_mysql';

-- 查看存储过程创建语句
SHOW CREATE PROCEDURE get_employee_by_id;

-- 查看函数创建语句
SHOW CREATE FUNCTION calculate_tax;

-- 删除存储过程
DROP PROCEDURE IF EXISTS variable_demo;

-- 删除函数
DROP FUNCTION IF EXISTS get_full_name;

-- 删除触发器
DROP TRIGGER IF EXISTS trg_employee_before_insert;


-- ============================================================
--                    总结
-- ============================================================

/*
存储过程：
- DELIMITER 更改结束符
- IN/OUT/INOUT 参数
- CALL 调用

变量与流程：
- DECLARE 声明变量
- SET / SELECT INTO 赋值
- IF/ELSEIF/ELSE/END IF
- CASE/WHEN/THEN/END CASE
- WHILE/REPEAT/LOOP

游标：
- DECLARE CURSOR FOR
- OPEN/FETCH/CLOSE
- HANDLER FOR NOT FOUND

函数：
- CREATE FUNCTION ... RETURNS
- DETERMINISTIC / READS SQL DATA
- 可在 SQL 中使用

触发器：
- BEFORE/AFTER INSERT/UPDATE/DELETE
- NEW.column / OLD.column
- 用于审计、验证、级联操作

错误处理：
- DECLARE HANDLER
- SIGNAL SQLSTATE
- GET DIAGNOSTICS

最佳实践：
- 保持存储过程简洁
- 使用事务保证一致性
- 适当的错误处理
- 注意性能影响
- 文档化复杂逻辑
*/

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734

procedures functions ​

SQL 脚本 ​

💬 讨论

procedures functions

SQL 脚本