Oracle触发器和MySQL触发器之间的区别

Posted 2022-04-18 sean-zou

Oracle触发器格式：

CREATE [OR REPLACE] TRIGGER trigger_name 
	BEFORE|AFTER INSERT|UPDATE|DELETE ON table_name 
	[FOR EACH ROW]
DECLARE arg_name type [CONSTANT] [NOT NULL] [:=value] 
BEGIN
	pl/sql语句
END

mysql触发器格式：

CREATE TRIGGER trigger_name
	BEFORE|AFTER INSERT|UPDATE|DELETE ON table_name
 	[FOR EACH ROW]
BEGIN
DECLARE arg_name1[,arg_name2,...] type [DEFAULT value]
   	sql语句
END

创建测试表（建表语句适用于Oracle、MySQL）：

CREATE TABLE test(
  id            int,
  name          varchar(10),
  age           int,
  birthday      date,
  description   varchar(50),
  PRIMARY KEY (id)
);
CREATE TABLE test_log(
  id            int,
  dealtime      date,
  dealtype      varchar(10),
  PRIMARY KEY (`id`)
);

Oracle触发器和MySQL触发器的区别如下：

1，创建语句格式不同

Oracle：create or replace（Oracle客户端需要手动提交，MySQL客户端设置的自动提交）

SQL> CREATE OR REPLACE TRIGGER trigger_test_insert
  2         BEFORE INSERT ON test
  3         FOR EACH ROW
  4  BEGIN
  5         insert into test_log values(1,sysdate,'insert');
  6  END;
  7  /
 
Trigger created
 
SQL> insert into test(id, name) values(1, 'name');
 
1 row inserted
 
SQL> commit;
 
Commit complete
 
SQL> select * from test_log;
 
                                     ID DEALTIME    DEALTYPE
--------------------------------------- ----------- ----------
                                      1 2014/7/16 1 insert

MySQL：不包含or replace

mysql> delimiter $
CREATE TRIGGER trigger_test_insert  
	BEFORE INSERT ON test 
	FOR EACH ROW
BEGIN
	insert into test_log values(1,now(),'insert');
END$
delimiter ;
Query OK, 0 rows affected

mysql> insert into test(id, name) values(1, 'name');
Query OK, 1 row affected

mysql> select * from test_log;
+----+------------+----------+
| id | dealtime   | dealtype |
+----+------------+----------+
|  1 | 2014-07-16 | insert   |
+----+------------+----------+
1 row in set

2，变量的声明位置、声明格式均不相同

Oracle：声明位置在触发时的执行语句块外部

通过%type的方式将变量与表特定字段类型相关联的好处是：在某些情况下，修改该字段类型时不需要修改触发器（如：字段类型由varchar(10)修改为varchar(20)时，不需要修改触发器）

SQL> CREATE TRIGGER trigger_test_insert
  2         BEFORE INSERT ON test
  3         FOR EACH ROW
  4  DECLARE id1 int default 1;
  5          id2 int:=1;
  6          id3 test_log.id%type:=1;
  7  BEGIN
  8          insert into test_log values(id1+id2+id3,sysdate,'insert');
  9  END;
 10  /
 
Trigger created
 
SQL> insert into test(id, name) values(1, 'name');
 
1 row inserted
 
SQL> commit;
 
Commit complete
 
SQL> select * from test_log;
 
                                     ID DEALTIME    DEALTYPE
--------------------------------------- ----------- ----------
                                      3 2014/7/16 1 insert

MySQL：声明位置在触发时的执行语句块内部

mysql> delimiter $
CREATE TRIGGER trigger_test_insert  
	BEFORE INSERT ON test 
	FOR EACH ROW
BEGIN
	DECLARE id1 int DEFAULT 1;
	DECLARE id2 int DEFAULT 1;
	insert into test_log values(id1+id2,now(),'insert');
END$
delimiter ;

Query OK, 0 rows affected

mysql> insert into test(id, name) values(1, 'name');
Query OK, 1 row affected

mysql> select * from test_log;
+----+------------+----------+
| id | dealtime   | dealtype |
+----+------------+----------+
|  2 | 2014-07-16 | insert   |
+----+------------+----------+
1 row in set

3，注释符不同

Oracle：使用/* */作为注释符，或者两个连续的-作为注释符（PL/SQL块中至少包含一条可执行语句）

CREATE OR REPLACE TRIGGER trigger_test_insert  
	BEFORE INSERT ON test 
	FOR EACH ROW
BEGIN
	--just a test
  /* just a test */
	null;
END;
/

MySQL：使用/* */作为注释符，或者两个连续的-后加一个空格作为注释符

delimiter $
CREATE TRIGGER trigger_test_insert  
	BEFORE INSERT ON test 
	FOR EACH ROW
BEGIN
	/* just a test */
	-- 两个‘-’后面必须带空格
END$
delimiter ;

4，赋值语法不同

Oracle：可以通过select into语句赋值，还可以通过:=进行赋值

SQL> CREATE OR REPLACE TRIGGER trigger_test_insert
  2  	BEFORE INSERT ON test
  3  	FOR EACH ROW
  4  DECLARE id int;
  5  BEGIN
  6  	select max(tl.id) into id from test_log tl;
  7  	if id is null then
  8  		id:=1;
  9  	else
 10  		id:=id+1;
 11  	end if;
 12  	insert into test_log values(id,sysdate,'insert');
 13  END;
 14  /
 
Trigger created
 
SQL> insert into test(id, name) values(1, 'name');
 
1 row inserted
 
SQL> commit;
 
Commit complete
 
SQL> select * from test_log;
 
                                     ID DEALTIME    DEALTYPE
--------------------------------------- ----------- ----------
                                      1 2014/7/16 1 insert

MySQL：可以通过select into语句赋值，还可以通过set语句进行赋值

mysql> delimiter $
CREATE TRIGGER trigger_test_insert  
	BEFORE INSERT ON test 
	FOR EACH ROW
BEGIN
	DECLARE id int;
	select max(tl.id) into id from test_log tl;
	if id is null then 
		set id=1;
	else 
		set id=id+1;
	end if;
	insert into test_log values(id,now(),'insert');
END$
delimiter ;

Query OK, 0 rows affected

mysql> insert into test(id, name) values(1, 'name');
Query OK, 1 row affected

mysql> select * from test_log;
+----+------------+----------+
| id | dealtime   | dealtype |
+----+------------+----------+
|  1 | 2014-07-16 | insert   |
+----+------------+----------+
1 row in set

5，对于行级更新触发器

Oracle：原有行用:old表示，新行用:new表示

SQL> CREATE OR REPLACE TRIGGER trigger_test_update
  2         BEFORE UPDATE ON test
  3         FOR EACH ROW
  4  BEGIN
  5         :new.description := 'change name[' ||
  6                          :old.name || ']->[' ||
  7                          :new.name || ']';
  8  END;
  9  /
 
Trigger created
 
SQL> insert into test(id, name) values (1, 'aaa');
 
1 row inserted
 
SQL> commit;
 
Commit complete
 
SQL> update test set name = 'bbb' where id = 1;
 
1 row updated
 
SQL> commit;
 
Commit complete
 
SQL> select id, name, description from test;
 
                                     ID NAME       DESCRIPTION
--------------------------------------- ---------- ----------------------                                      
                                      1 bbb        change name[aaa]->[bbb]

MySQL：原有行用old表示，新行用new表示

mysql> delimiter $
CREATE TRIGGER trigger_test_update  
	BEFORE UPDATE ON test 
	FOR EACH ROW
BEGIN
	set new.description = concat('change name[',
		old.name,']->[',new.name,']');
END$
delimiter ;

Query OK, 0 rows affected

mysql> insert into test(id, name) values (1, 'aaa');
Query OK, 1 row affected

mysql> update test set name = 'bbb' where id = 1;
Query OK, 1 row affected
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select id, name, description from test;
+----+------+-------------------------+
| id | name | description             |
+----+------+-------------------------+
|  1 | bbb  | change name[aaa]->[bbb] |
+----+------+-------------------------+
1 row in set

6，其它一些语法、函数上的区别

Oracle：使用if...elsif...else

MySQL：使用if...elseif...else

Oracle：sysdate指代系统时间

MySQL：sysdate()指代系统时间