一、MySQL触发器

　　触发器是由MySQL的基本命令事件来触发某种特定操作，这些基本的命令由INSERT、UPDATE、DELETE等事件来触发某些特定操作。满足触发器的触发条件时，数据库系统就会自动执行触发器中定义的程序语句。这样可以令某些操作之间的一致性得到协调。

　　1.创建MySQL触发器　　

  1. mysql> CREATE TABLE IF NOT EXISTS tb_booklog(
  2.     -> id int(11) PRIMARY KEY auto_increment NOT NULL,
  3.     -> event varchar(200) NOT NULL,
  4.     -> logtime timestamp NOT NULL DEFAULT current_timestamp
  5.     -> );
  6. Query OK, 0 rows affected (0.03 sec)
  7.  
  8. mysql> DELIMITER //
  9. mysql> CREATE TRIGGER auto_save_log BEFORE INSERT
  10.     -> ON tb_bookinfo FOR EACH ROW
  11.     -> INSERT INTO tb_booklog(event,logtime) values('look at me',now());
  12.     -> //
  13. Query OK, 0 rows affected (0.01 sec)
  1. mysql> SELECT * FROM tb_bookinfo;
  2.     -> //
  3. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  4. | barcode  | bookname  | typeid | author    | ISBN | price | page | bookcase | inTime     | del  | id |
  5. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  6. | 17120107 | Java King |      3 | LianJiang | 115  | 49.80 |  350 |        1 | 2018-04-17 |    0 |  1 |
  7. | 17120108 | Lian      |      1 | QiaoJiang | 116  | 50.00 |  351 |        2 | 2018-04-18 |    0 |  2 |
  8. | 17120109 | Tian King |      2 | TianJiang | 117  | 51.10 |  352 |        3 | 2018-04-19 |    0 |  3 |
  9. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  10. 3 rows in set (0.00 sec)
  1. mysql> INSERT INTO tb_bookinfo
  2.     -> (barcode,bookname,typeid,author,ISBN,price,page,bookcase,inTime,del,id)
  3.     -> VALUES
  4.     -> ('17120110','ShenOba',4,'ShenJiang','118',52.15,300,4,'2018-04-20',0,4);
  5.     -> //
  6. Query OK, 1 row affected (0.00 sec)
  7.  
  8. mysql> SELECT * FROM tb_bookinfo;
  9.     -> //
  10. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  11. | barcode  | bookname  | typeid | author    | ISBN | price | page | bookcase | inTime     | del  | id |
  12. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  13. | 17120107 | Java King |      3 | LianJiang | 115  | 49.80 |  350 |        1 | 2018-04-17 |    0 |  1 |
  14. | 17120108 | Lian      |      1 | QiaoJiang | 116  | 50.00 |  351 |        2 | 2018-04-18 |    0 |  2 |
  15. | 17120109 | Tian King |      2 | TianJiang | 117  | 51.10 |  352 |        3 | 2018-04-19 |    0 |  3 |
  16. | 17120110 | ShenOba   |      4 | ShenJiang | 118  | 52.15 |  300 |        4 | 2018-04-20 |    0 |  4 |
  17. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  18. 4 rows in set (0.00 sec)
  19.  
  20. mysql> SELECT * FROM tb_booklog;
  21.     -> //
  22. +----+------------+---------------------+
  23. | id | event      | logtime             |
  24. +----+------------+---------------------+
  25. |  2 | look at me | 2018-04-18 19:40:02 |
  26. +----+------------+---------------------+
  27. 1 row in set (0.00 sec)

　　2.创建具有多个执行语句的触发器

  1. mysql> CREATE DEFINER=`root`@`localhost` TRIGGER delete_book_info BEFORE DELETE
  2.     -> ON tb_bookinfo FOR EACH ROW
  3.     -> BEGIN
  4.     -> INSERT INTO tb_booklog(event,logtime) values('let me go',now());
  5.     -> INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  6.     -> END
  7.     -> //
  8. Query OK, 0 rows affected (0.01 sec)

　　血一般惨痛的教训！！！当删除表中某一条记录未能成功时，检查一下触发器什么的有没有INSERT INTO语句，如果有，检查插入值的个数和表能不能对应起来，这里的原因就是两个表不一致！！！

  1. Microsoft Windows [版本 10.0.16299.371]
  2. (c) 2017 Microsoft Corporation。保留所有权利。
  3.  
  4. C:\Users\BigJun>mysql -uroot -p
  5. Enter password: *********
  6. Welcome to the MySQL monitor.  Commands end with ; or \g.
  7. Your MySQL connection id is 23
  8. Server version: 5.7.20 MySQL Community Server (GPL)
  9.  
  10. Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
  11.  
  12. Oracle is a registered trademark of Oracle Corporation and/or its
  13. affiliates. Other names may be trademarks of their respective
  14. owners.
  15.  
  16. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  17.  
  18. mysql> DELIMITER //
  19. mysql> CREATE DEFINER=`root`@`localhost` TRIGGER BEFORE DELETE
  20.     -> ON tb_bookinfo FOR EACH ROW
  21.     -> BEGIN
  22.     -> INSERT INTO tb_booklog(event,logtime) values('let me go'.now());
  23.     -> INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  24.     -> END
  25.     -> //
  26. ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'BEFORE DELETE
  27. ON tb_bookinfo FOR EACH ROW
  28. BEGIN
  29. INSERT INTO tb_booklog(event,log' at line 1
  30. mysql> CREATE DEFINER=`root`@`localhost` TRIGGER delete_book_info BEFORE DELETE
  31.     -> ON tb_bookinfo FOR EACH ROW
  32.     -> BEGIN
  33.     -> INSERT INTO tb_booklog(event,logtime) values('let me go'.now());
  34.     -> INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  35.     -> END
  36.     -> //
  37. ERROR 1046 (3D000): No database selected
  38. mysql> use db_library;
  39. ERROR 1049 (42000): Unknown database 'db_library;'
  40. mysql> USE db_library;
  41. ERROR 1049 (42000): Unknown database 'db_library;'
  42. mysql> exit
  43. Bye
  44.  
  45. C:\Users\BigJun>mysql -uroot -p
  46. Enter password: *********
  47. Welcome to the MySQL monitor.  Commands end with ; or \g.
  48. Your MySQL connection id is 24
  49. Server version: 5.7.20 MySQL Community Server (GPL)
  50.  
  51. Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
  52.  
  53. Oracle is a registered trademark of Oracle Corporation and/or its
  54. affiliates. Other names may be trademarks of their respective
  55. owners.
  56.  
  57. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  58.  
  59. mysql> show databases;
  60. +--------------------+
  61. | Database           |
  62. +--------------------+
  63. | information_schema |
  64. | db_database13      |
  65. | db_library         |
  66. | db_library1        |
  67. | db_library_gbk     |
  68. | hotel              |
  69. | mybatis            |
  70. | mysql              |
  71. | mysqldb            |
  72. | performance_schema |
  73. | se                 |
  74. | spring             |
  75. | springapp          |
  76. | sys                |
  77. | test               |
  78. +--------------------+
  79. 15 rows in set (0.00 sec)
  80.  
  81. mysql> use db_library;
  82. Database changed
  83. mysql> DELIMITER //
  84. mysql> CREATE DEFINER=`root`@`localhost` TRIGGER delete_book_info BEFORE DELETE
  85.     -> ON tb_bookinfo FOR EACH ROW
  86.     -> BEGIN
  87.     -> INSERT INTO tb_booklog(event,logtime) values('let me go'.now());
  88.     ->
  89.     -> INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  90.     -> END
  91.     -> //
  92. ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '.now());
  93.  
  94. INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  95. ' at line 4
  96. mysql> CREATE DEFINER=`root`@`localhost` TRIGGER delete_book_info BEFORE DELETE
  97.     -> ON tb_bookinfo FOR EACH ROW
  98.     -> BEGIN
  99.     -> INSERT INTO tb_booklog(event,logtime) values('let me go'.now());
  100.     -> INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  101.     -> END
  102.     -> //
  103. ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '.now());
  104. INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  105. E' at line 4
  106. mysql> CREATE DEFINER=`root`@`localhost` TRIGGER delete_book_info BEFORE DELETE
  107.     -> ON tb_bookinfo FOR EACH ROW
  108.     -> BEGIN
  109.     -> INSERT INTO tb_booklog(event,logtime) values('let me go',now());
  110.     -> INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  111.     -> END
  112.     -> //
  113. Query OK, 0 rows affected (0.01 sec)
  114.  
  115. mysql> select * from tb_bookinfo;
  116.     -> //
  117. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  118. | barcode  | bookname  | typeid | author    | ISBN | price | page | bookcase | inTime     | del  | id |
  119. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  120. | 17120107 | Java King |      3 | LianJiang | 115  | 49.80 |  350 |        1 | 2018-04-17 |    0 |  1 |
  121. | 17120108 | Lian      |      1 | QiaoJiang | 116  | 50.00 |  351 |        2 | 2018-04-18 |    0 |  2 |
  122. | 17120109 | Tian King |      2 | TianJiang | 117  | 51.10 |  352 |        3 | 2018-04-19 |    0 |  3 |
  123. | 17120110 | ShenOba   |      4 | ShenJiang | 118  | 52.15 |  300 |        4 | 2018-04-20 |    0 |  4 |
  124. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  125. 4 rows in set (0.01 sec)
  126.  
  127. mysql> select * from tb_booklog;
  128.     -> //
  129. +----+------------+---------------------+
  130. | id | event      | logtime             |
  131. +----+------------+---------------------+
  132. |  2 | look at me | 2018-04-18 19:40:02 |
  133. +----+------------+---------------------+
  134. 1 row in set (0.00 sec)
  135.  
  136. mysql> select * from tb_bookinfobak;
  137.     -> //
  138. Empty set (0.00 sec)
  139.  
  140. mysql> DELETE FROM tb_bookinfo where id=4;
  141.     -> //
  142. ERROR 1136 (21S01): Column count doesn't match value count at row 1
  143. mysql> DELETE FROM tb_bookinfo WHERE id=4;
  144.     -> //
  145. ERROR 1136 (21S01): Column count doesn't match value count at row 1
  146. mysql> DELETE FROM tb_bookinfo WHERE id=3;
  147.     -> //
  148. ERROR 1136 (21S01): Column count doesn't match value count at row 1
  149. mysql> DELETE FROM tb_bookinfo WHERE barcode='17120107';
  150.     -> //
  151. ERROR 1136 (21S01): Column count doesn't match value count at row 1
  152. mysql> show triggers;
  153.     -> //
  154. +------------------+--------+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------+--------+------------------------+-------------------------------------------------------------------------------------------------------------------------------------------+----------------+----------------------+----------------------+--------------------+
  155. | Trigger          | Event  | Table       | Statement                                                                                                                                        | Timing | Created                | sql_mode                                                                                                                                  | Definer        | character_set_client | collation_connection | Database Collation |
  156. +------------------+--------+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------+--------+------------------------+-------------------------------------------------------------------------------------------------------------------------------------------+----------------+----------------------+----------------------+--------------------+
  157. | delete_book_info | DELETE | tb_bookinfo | BEGIN
  158. INSERT INTO tb_booklog(event,logtime) values('let me go',now());
  159. INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  160. END | BEFORE | 2018-04-18 20:35:07.19 | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | root@localhost | gbk                  | gbk_chinese_ci       | utf8_general_ci    |
  161. +------------------+--------+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------+--------+------------------------+-------------------------------------------------------------------------------------------------------------------------------------------+----------------+----------------------+----------------------+--------------------+
  162. 1 row in set (0.00 sec)
  163.  
  164. mysql> select * from tb_bookinfo;
  165.     -> //
  166. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  167. | barcode  | bookname  | typeid | author    | ISBN | price | page | bookcase | inTime     | del  | id |
  168. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  169. | 17120107 | Java King |      3 | LianJiang | 115  | 49.80 |  350 |        1 | 2018-04-17 |    0 |  1 |
  170. | 17120108 | Lian      |      1 | QiaoJiang | 116  | 50.00 |  351 |        2 | 2018-04-18 |    0 |  2 |
  171. | 17120109 | Tian King |      2 | TianJiang | 117  | 51.10 |  352 |        3 | 2018-04-19 |    0 |  3 |
  172. | 17120110 | ShenOba   |      4 | ShenJiang | 118  | 52.15 |  300 |        4 | 2018-04-20 |    0 |  4 |
  173. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  174. 4 rows in set (0.00 sec)
  175.  
  176. mysql> delete from tb_bookinfo where id=1;
  177.     -> //
  178. ERROR 1136 (21S01): Column count doesn't match value count at row 1
  179. mysql> desc tb_bookinfobak;
  180.     -> //
  181. +------------+------------------+------+-----+---------+-------+
  182. | Field      | Type             | Null | Key | Default | Extra |
  183. +------------+------------------+------+-----+---------+-------+
  184. | barcode    | varchar(30)      | YES  |     | NULL    |       |
  185. | bookname   | varchar(70)      | YES  |     | NULL    |       |
  186. | typeid     | int(10) unsigned | YES  |     | NULL    |       |
  187. | author     | varchar(30)      | YES  |     | NULL    |       |
  188. | ISBN       | varchar(20)      | YES  |     | NULL    |       |
  189. | price      | float(8,2)       | YES  |     | NULL    |       |
  190. | page       | int(10) unsigned | YES  |     | NULL    |       |
  191. | bookcase   | int(10) unsigned | YES  |     | NULL    |       |
  192. | inTime     | datetime(6)      | YES  |     | NULL    |       |
  193. | del        | tinyint(1)       | YES  |     | 0       |       |
  194. | id         | int(11)          | NO   |     | NULL    |       |
  195. | translator | varchar(30)      | NO   |     | NULL    |       |
  196. +------------+------------------+------+-----+---------+-------+
  197. 12 rows in set (0.00 sec)
  198.  
  199. mysql> alter table tb_bookinfobak drop transtor;
  200.     -> //
  201. ERROR 1091 (42000): Can't DROP 'transtor'; check that column/key exists
  202. mysql> alter table tb_bookinfobak drop translator;
  203.     -> //
  204. Query OK, 0 rows affected (0.04 sec)
  205. Records: 0  Duplicates: 0  Warnings: 0
  206.  
  207. mysql> desc tb_bookinfobak;
  208.     -> //
  209. +----------+------------------+------+-----+---------+-------+
  210. | Field    | Type             | Null | Key | Default | Extra |
  211. +----------+------------------+------+-----+---------+-------+
  212. | barcode  | varchar(30)      | YES  |     | NULL    |       |
  213. | bookname | varchar(70)      | YES  |     | NULL    |       |
  214. | typeid   | int(10) unsigned | YES  |     | NULL    |       |
  215. | author   | varchar(30)      | YES  |     | NULL    |       |
  216. | ISBN     | varchar(20)      | YES  |     | NULL    |       |
  217. | price    | float(8,2)       | YES  |     | NULL    |       |
  218. | page     | int(10) unsigned | YES  |     | NULL    |       |
  219. | bookcase | int(10) unsigned | YES  |     | NULL    |       |
  220. | inTime   | datetime(6)      | YES  |     | NULL    |       |
  221. | del      | tinyint(1)       | YES  |     | 0       |       |
  222. | id       | int(11)          | NO   |     | NULL    |       |
  223. +----------+------------------+------+-----+---------+-------+
  224. 11 rows in set (0.00 sec)
  225.  
  226. mysql> desc tb_bookinfo;
  227.     -> //
  228. +----------+------------------+------+-----+---------+-------+
  229. | Field    | Type             | Null | Key | Default | Extra |
  230. +----------+------------------+------+-----+---------+-------+
  231. | barcode  | varchar(30)      | YES  |     | NULL    |       |
  232. | bookname | varchar(70)      | YES  |     | NULL    |       |
  233. | typeid   | int(10) unsigned | YES  |     | NULL    |       |
  234. | author   | varchar(30)      | YES  |     | NULL    |       |
  235. | ISBN     | varchar(20)      | YES  |     | NULL    |       |
  236. | price    | float(8,2)       | YES  |     | NULL    |       |
  237. | page     | int(10) unsigned | YES  |     | NULL    |       |
  238. | bookcase | int(10) unsigned | YES  |     | NULL    |       |
  239. | inTime   | date             | YES  |     | NULL    |       |
  240. | del      | tinyint(1)       | YES  |     | 0       |       |
  241. | id       | int(11)          | NO   | PRI | NULL    |       |
  242. +----------+------------------+------+-----+---------+-------+
  243. 11 rows in set (0.00 sec)
  244.  
  245. mysql> alter table tb_bookinfobak modify inTime date;
  246.     -> //
  247. Query OK, 0 rows affected (0.04 sec)
  248. Records: 0  Duplicates: 0  Warnings: 0
  249.  
  250. mysql> desc tb_bookinfobak;
  251.     -> //
  252. +----------+------------------+------+-----+---------+-------+
  253. | Field    | Type             | Null | Key | Default | Extra |
  254. +----------+------------------+------+-----+---------+-------+
  255. | barcode  | varchar(30)      | YES  |     | NULL    |       |
  256. | bookname | varchar(70)      | YES  |     | NULL    |       |
  257. | typeid   | int(10) unsigned | YES  |     | NULL    |       |
  258. | author   | varchar(30)      | YES  |     | NULL    |       |
  259. | ISBN     | varchar(20)      | YES  |     | NULL    |       |
  260. | price    | float(8,2)       | YES  |     | NULL    |       |
  261. | page     | int(10) unsigned | YES  |     | NULL    |       |
  262. | bookcase | int(10) unsigned | YES  |     | NULL    |       |
  263. | inTime   | date             | YES  |     | NULL    |       |
  264. | del      | tinyint(1)       | YES  |     | 0       |       |
  265. | id       | int(11)          | NO   |     | NULL    |       |
  266. +----------+------------------+------+-----+---------+-------+
  267. 11 rows in set (0.00 sec)
  268.  
  269. mysql> select * from tb_bookinfo;
  270.     -> //
  271. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  272. | barcode  | bookname  | typeid | author    | ISBN | price | page | bookcase | inTime     | del  | id |
  273. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  274. | 17120107 | Java King |      3 | LianJiang | 115  | 49.80 |  350 |        1 | 2018-04-17 |    0 |  1 |
  275. | 17120108 | Lian      |      1 | QiaoJiang | 116  | 50.00 |  351 |        2 | 2018-04-18 |    0 |  2 |
  276. | 17120109 | Tian King |      2 | TianJiang | 117  | 51.10 |  352 |        3 | 2018-04-19 |    0 |  3 |
  277. | 17120110 | ShenOba   |      4 | ShenJiang | 118  | 52.15 |  300 |        4 | 2018-04-20 |    0 |  4 |
  278. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  279. 4 rows in set (0.00 sec)
  280.  
  281. mysql> select * from tb_bookbak;
  282.     -> //
  283. ERROR 1146 (42S02): Table 'db_library.tb_bookbak' doesn't exist
  284. mysql> select * from tb_bookinfobak;
  285.     -> //
  286. Empty set (0.00 sec)
  287.  
  288. mysql> select * from tb_booklog;
  289.     -> //
  290. +----+------------+---------------------+
  291. | id | event      | logtime             |
  292. +----+------------+---------------------+
  293. |  2 | look at me | 2018-04-18 19:40:02 |
  294. +----+------------+---------------------+
  295. 1 row in set (0.00 sec)
  296.  
  297. mysql> delete from tb_bookinfo where id=1;
  298.     -> //
  299. Query OK, 1 row affected (0.01 sec)
  300.  
  301. mysql> select * from tb_bookinfobak;
  302.     -> //
  303. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  304. | barcode  | bookname  | typeid | author    | ISBN | price | page | bookcase | inTime     | del  | id |
  305. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  306. | 17120107 | Java King |      3 | LianJiang | 115  | 49.80 |  350 |        1 | 2018-04-17 |    0 |  1 |
  307. +----------+-----------+--------+-----------+------+-------+------+----------+------------+------+----+
  308. 1 row in set (0.00 sec)
  309.  
  310. mysql> select * from tb_booklog;
  311.     -> //
  312. +----+------------+---------------------+
  313. | id | event      | logtime             |
  314. +----+------------+---------------------+
  315. |  2 | look at me | 2018-04-18 19:40:02 |
  316. |  8 | let me go  | 2018-04-18 20:54:19 |
  317. +----+------------+---------------------+
  318. 2 rows in set (0.00 sec)

　　二、查看触发器

　　1.SHOW TRIGGER语句

  1. mysql> SHOW TRIGGERs\G
  2. *************************** 1. row ***************************
  3.              Trigger: delete_book_info
  4.                Event: DELETE
  5.                Table: tb_bookinfo
  6.            Statement: BEGIN
  7. INSERT INTO tb_booklog(event,logtime) values('let me go',now());
  8. INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  9. END
  10.               Timing: BEFORE
  11.              Created: 2018-04-18 20:35:07.19
  12.             sql_mode: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
  13.              Definer: root@localhost
  14. character_set_client: gbk
  15. collation_connection: gbk_chinese_ci
  16.   Database Collation: utf8_general_ci
  17. 1 row in set (0.00 sec)

　　2.查看triggers表中的触发信息

　　（1）查看所有触发器的定义

  1. mysql> SELECT * FROM information_schema.triggers\G
  2. *************************** 1. row ***************************
  3.            TRIGGER_CATALOG: def
  4.             TRIGGER_SCHEMA: db_library
  5.               TRIGGER_NAME: delete_book_info
  6.         EVENT_MANIPULATION: DELETE
  7.       EVENT_OBJECT_CATALOG: def
  8.        EVENT_OBJECT_SCHEMA: db_library
  9.         EVENT_OBJECT_TABLE: tb_bookinfo
  10.               ACTION_ORDER: 1
  11.           ACTION_CONDITION: NULL
  12.           ACTION_STATEMENT: BEGIN
  13. INSERT INTO tb_booklog(event,logtime) values('let me go',now());
  14. INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  15. END
  16.         ACTION_ORIENTATION: ROW
  17.              ACTION_TIMING: BEFORE
  18. ACTION_REFERENCE_OLD_TABLE: NULL
  19. ACTION_REFERENCE_NEW_TABLE: NULL
  20.   ACTION_REFERENCE_OLD_ROW: OLD
  21.   ACTION_REFERENCE_NEW_ROW: NEW
  22.                    CREATED: 2018-04-18 20:35:07.19
  23.                   SQL_MODE: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
  24.                    DEFINER: root@localhost
  25.       CHARACTER_SET_CLIENT: gbk
  26.       COLLATION_CONNECTION: gbk_chinese_ci
  27.         DATABASE_COLLATION: utf8_general_ci
  28. *************************** 2. row ***************************
  29.            TRIGGER_CATALOG: def
  30.             TRIGGER_SCHEMA: sys
  31.               TRIGGER_NAME: sys_config_insert_set_user
  32.         EVENT_MANIPULATION: INSERT
  33.       EVENT_OBJECT_CATALOG: def
  34.        EVENT_OBJECT_SCHEMA: sys
  35.         EVENT_OBJECT_TABLE: sys_config
  36.               ACTION_ORDER: 1
  37.           ACTION_CONDITION: NULL
  38.           ACTION_STATEMENT: BEGIN IF @sys.ignore_sys_config_triggers != true AND NEW.set_by IS NULL THEN SET NEW.set_by = USER(); END IF; END
  39.         ACTION_ORIENTATION: ROW
  40.              ACTION_TIMING: BEFORE
  41. ACTION_REFERENCE_OLD_TABLE: NULL
  42. ACTION_REFERENCE_NEW_TABLE: NULL
  43.   ACTION_REFERENCE_OLD_ROW: OLD
  44.   ACTION_REFERENCE_NEW_ROW: NEW
  45.                    CREATED: 2018-01-08 16:14:42.70
  46.                   SQL_MODE:
  47.                    DEFINER: mysql.sys@localhost
  48.       CHARACTER_SET_CLIENT: utf8
  49.       COLLATION_CONNECTION: utf8_general_ci
  50.         DATABASE_COLLATION: utf8_general_ci
  51. *************************** 3. row ***************************
  52.            TRIGGER_CATALOG: def
  53.             TRIGGER_SCHEMA: sys
  54.               TRIGGER_NAME: sys_config_update_set_user
  55.         EVENT_MANIPULATION: UPDATE
  56.       EVENT_OBJECT_CATALOG: def
  57.        EVENT_OBJECT_SCHEMA: sys
  58.         EVENT_OBJECT_TABLE: sys_config
  59.               ACTION_ORDER: 1
  60.           ACTION_CONDITION: NULL
  61.           ACTION_STATEMENT: BEGIN IF @sys.ignore_sys_config_triggers != true AND NEW.set_by IS NULL THEN SET NEW.set_by = USER(); END IF; END
  62.         ACTION_ORIENTATION: ROW
  63.              ACTION_TIMING: BEFORE
  64. ACTION_REFERENCE_OLD_TABLE: NULL
  65. ACTION_REFERENCE_NEW_TABLE: NULL
  66.   ACTION_REFERENCE_OLD_ROW: OLD
  67.   ACTION_REFERENCE_NEW_ROW: NEW
  68.                    CREATED: 2018-01-08 16:14:42.70
  69.                   SQL_MODE:
  70.                    DEFINER: mysql.sys@localhost
  71.       CHARACTER_SET_CLIENT: utf8
  72.       COLLATION_CONNECTION: utf8_general_ci
  73.         DATABASE_COLLATION: utf8_general_ci
  74. 3 rows in set (0.03 sec)

　　（2）查看指定触发器名称的触发器的定义（指定数据库时将NAME改成SCHEMA，等号后面改成数据库名）

  1. mysql> SELECT * FROM information_schema.triggers WHERE TRIGGER_NAME='delete_book_info'\G;
  2. *************************** 1. row ***************************
  3.            TRIGGER_CATALOG: def
  4.             TRIGGER_SCHEMA: db_library
  5.               TRIGGER_NAME: delete_book_info
  6.         EVENT_MANIPULATION: DELETE
  7.       EVENT_OBJECT_CATALOG: def
  8.        EVENT_OBJECT_SCHEMA: db_library
  9.         EVENT_OBJECT_TABLE: tb_bookinfo
  10.               ACTION_ORDER: 1
  11.           ACTION_CONDITION: NULL
  12.           ACTION_STATEMENT: BEGIN
  13. INSERT INTO tb_booklog(event,logtime) values('let me go',now());
  14. INSERT INTO tb_bookinfobak SELECT * FROM tb_bookinfo where id=OLD.id;
  15. END
  16.         ACTION_ORIENTATION: ROW
  17.              ACTION_TIMING: BEFORE
  18. ACTION_REFERENCE_OLD_TABLE: NULL
  19. ACTION_REFERENCE_NEW_TABLE: NULL
  20.   ACTION_REFERENCE_OLD_ROW: OLD
  21.   ACTION_REFERENCE_NEW_ROW: NEW
  22.                    CREATED: 2018-04-18 20:35:07.19
  23.                   SQL_MODE: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
  24.                    DEFINER: root@localhost
  25.       CHARACTER_SET_CLIENT: gbk
  26.       COLLATION_CONNECTION: gbk_chinese_ci
  27.         DATABASE_COLLATION: utf8_general_ci
  28. 1 row in set (0.01 sec)

　　三、使用触发器

　　1.触发器的执行顺序

  1. mysql> create table if not exists tb_temp(
  2.     -> id int(11) PRIMARY KEY auto_increment NOT NULL,
  3.     -> event varchar(200) NOT NULL,
  4.     -> time timestamp NOT NULL DEFAULT current_timestamp
  5.     -> );
  6. Query OK, 0 rows affected (0.03 sec)
  1. mysql> create table tb_bookcase(
  2.     -> id int(11) PRIMARY KEY auto_increment NOT NULL,
  3.     -> name varchar(200)
  4.     -> );
  5. Query OK, 0 rows affected (0.02 sec)
  6.  
  7. mysql> create trigger before_in BEFORE INSERT ON
  8.     -> tb_bookcase FOR EACH ROW
  9.     -> INSERT INTO tb_temp(event) values('BEFORE INSERT');
  10. Query OK, 0 rows affected (0.01 sec)
  11.  
  12. mysql> create trigger after_in AFTER INSERT ON
  13.     -> tb_bookcase FOR EACH ROW
  14.     -> INSERT INTO tb_temp(event) values('AFTER INSERT');
  15. Query OK, 0 rows affected (0.01 sec)
  16.  
  17. mysql> select * from tb_bookcase;
  18. Empty set (0.00 sec)
  19.  
  20. mysql> select * from tb_temp;
  21. Empty set (0.00 sec)
  22.  
  23. mysql> INSERT INTO tb_bookcase(name) VALUES('左边第二个');
  24. Query OK, 1 row affected (0.01 sec)
  25.  
  26. mysql> select * from tb_bookcase;
  27. +----+-----------------+
  28. | id | name            |
  29. +----+-----------------+
  30. |  1 | 左边第二个      |
  31. +----+-----------------+
  32. 1 row in set (0.00 sec)
  33.  
  34. mysql> select * from tb_temp;
  35. +----+---------------+---------------------+
  36. | id | event         | time                |
  37. +----+---------------+---------------------+
  38. |  1 | BEFORE INSERT | 2018-04-19 08:17:28 |
  39. |  2 | AFTER INSERT  | 2018-04-19 08:17:28 |
  40. +----+---------------+---------------------+
  41. 2 rows in set (0.00 sec)

　　2.使用触发器维护冗余数据（为了避免数据不一致问题的发生，尽量不要人工维护数据，建议通过编程自动维护）

  1. mysql> create table tb_stock(
  2.     -> id int(11) PRIMARY KEY auto_increment NOT NULL.
  3.     -> id int(11) PRIMARY KEY auto_increment NOT NULL.^C
  4. mysql> create table tb_stock(
  5.     -> id int(11) PRIMARY KEY auto_increment NOT NULL,
  6.     -> goodsname varchar(200) NOT NULL,
  7.     -> number int(11)
  8.     -> );
  9. Query OK, 0 rows affected (0.02 sec)
  1. mysql> select * from tb_stock;
  2. +----+-------------+--------+
  3. | id | goodsname   | number |
  4. +----+-------------+--------+
  5. |  1 | 小猪佩qi    |    100 |
  6. +----+-------------+--------+
  7. 1 row in set (0.00 sec)
  1. mysql> create table tb_sell(
  2.     -> id int(11) PRIMARY KEY auto_increment NOT NULL,
  3.     -> goodsname varchar(200),
  4.     -> number int(11)
  5.     -> );
  6.     -> //
  7. Query OK, 0 rows affected (0.02 sec)
  8.  
  9. mysql> select * from tb_sell;
  10.     -> //
  11. Empty set (0.00 sec)
  1. mysql> CREATE TRIGGER auto_number AFTER INSERT
  2.     -> ON tb_sell FOR EACH ROW
  3.     -> BEGIN
  4.     -> DECLARE sellnum int(10);
  5.     -> SELECT number FROM tb_sell where id=NEW.id INTO @sellnum;
  6.     -> UPDATE tb_stock SET number=number-@sellnum WHERE goodsname='小猪佩qi';
  7.     -> END
  8.     -> //
  9. Query OK, 0 rows affected (0.01 sec)
  1. mysql> INSERT INTO tb_sell(goodsname,number) VALUES
  2.     -> ('小猪佩qi',2);
  3.     -> //
  4. Query OK, 1 row affected (0.01 sec)
  5.  
  6. mysql> select * from tb_sell;
  7.     -> //
  8. +----+-------------+--------+
  9. | id | goodsname   | number |
  10. +----+-------------+--------+
  11. |  1 | 小猪佩qi    |      2 |
  12. +----+-------------+--------+
  13. 1 row in set (0.00 sec)
  14.  
  15. mysql> select * from tb_stock;
  16.     -> //
  17. +----+-------------+--------+
  18. | id | goodsname   | number |
  19. +----+-------------+--------+
  20. |  1 | 小猪佩qi    |     98 |
  21. +----+-------------+--------+
  22. 1 row in set (0.00 sec)

　　四、删除触发器

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