1-连接数据库：
mysql -h localhost -u jiangbiao -p
xxxxx@xxx:~$ mysql -h localhost -u jiangbiao -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2444832
Server version: 5.5.40-log Source distribution
2-显示表的信息，包括所用引擎，对于mysql，只有InnoDB引擎支持触发器操作
SHOW CREATE TABLE tbl_buniness;
3-显示数据库 :
show databases;
4-使用数据库：
use databasename;
5-显示数据表：
show tables;
6-显示具体的表结构 :
describe tablename;
7-插入操作：
INSERT INTO `root_trigger` (`id`,`data`)
VALUES ('', 'test root line 1'),
('', 'test root line 2'),
('', 'test root line 3');
8 - 通过DELETE CASCADE外键约束的处理机制来处理级联删除操作：
-- 创建测试主表. ID 是主键.
CREATE TABLE test_main (
id INT NOT NULL,
value VARCHAR(10),
PRIMARY KEY(id)
); -- 创建测试子表.
CREATE TABLE test_sub (
id INT NOT NULL,
main_id INT ,
value VARCHAR(10),
PRIMARY KEY(id)
); -- 插入测试主表数据.
INSERT INTO test_main(id, value) VALUES (1, 'ONE');
INSERT INTO test_main(id, value) VALUES (2, 'TWO'); -- 插入测试子表数据.
INSERT INTO test_sub(id, main_id, value) VALUES (1, 1, 'ONEONE');
INSERT INTO test_sub(id, main_id, value) VALUES (2, 2, 'TWOTWO'); --- --通过 DELETE CASCADE 外键约束的处理机制来处理
mysql> ALTER TABLE test_sub
-> ADD CONSTRAINT main_id_cons
-> FOREIGN KEY (main_id)
-> REFERENCES test_main(id)
-> ON DELETE CASCADE//
Query OK, 2 rows affected (0.16 sec)
Records: 2 Duplicates: 0 Warnings: 0 mysql> DELETE FROM
-> test_main
-> WHERE
-> id = 1;
-> //
Query OK, 1 row affected (0.02 sec) mysql> SELECT
-> *
-> FROM
-> test_sub;
-> //
+----+---------+--------+
| id | main_id | value |
+----+---------+--------+
| 2 | 2 | TWOTWO |
+----+---------+--------+
1 row in set (0.00 sec)
9 - 如果你非要使用触发器来处理， 那么下面是一个例子：
-- 创建测试主表. ID 是主键.
CREATE TABLE t_test_main (
id INT NOT NULL,
value VARCHAR(10),
PRIMARY KEY(id)
); -- 创建测试子表.
CREATE TABLE t_test_sub (
id INT NOT NULL,
main_id INT ,
value VARCHAR(10),
PRIMARY KEY(id)
); -- 插入测试主表数据.
INSERT INTO t_test_main(id, value) VALUES (1, 'ONE');
INSERT INTO t_test_main(id, value) VALUES (2, 'TWO'); -- 插入测试子表数据.
INSERT INTO t_test_sub(id, main_id, value) VALUES (1, 1, 'ONEONE');
INSERT INTO t_test_sub(id, main_id, value) VALUES (2, 2, 'TWOTWO'); DELIMITER // CREATE TRIGGER tr_t_test_main_Del
BEFORE DELETE ON t_test_main
FOR EACH ROW
BEGIN
DELETE FROM t_test_sub WHERE main_id = OLD.id;
END;
// DELIMITER ; mysql> delete from t_test_main where id = 1;
Query OK, 1 row affected (0.01 sec) mysql> select * from t_test_sub;
+----+---------+--------+
| id | main_id | value |
+----+---------+--------+
| 2 | 2 | TWOTWO |
+----+---------+--------+
1 row in set (0.00 sec)
关于8、9两点的原文链接：https://zhidao.baidu.com/question/562372469.html10 - 其他：
这里有个已经整理的博客链接