openGauss学习笔记-42 openGauss 高级数据管理-触发器
触发器会在指定的数据库事件发生时自动执行函数。
42.1 语法格式
-
创建触发器
CREATE TRIGGER trigger_name { BEFORE | AFTER | INSTEAD OF } { event [ OR ... ] } ON table_name [ FOR [ EACH ] { ROW | STATEMENT } ] [ WHEN ( condition ) ] EXECUTE PROCEDURE function_name ( arguments );
-
修改触发器
ALTER TRIGGER trigger_name ON table_name RENAME TO new_trigger_name;
-
删除触发器
DROP TRIGGER trigger_name ON table_name [ CASCADE | RESTRICT ];
42.2 参数说明
-
trigger_name
触发器名称。
-
BEFORE
触发器函数是在触发事件发生前执行。
-
AFTER
触发器函数是在触发事件发生后执行。
-
INSTEAD OF
触发器函数直接替代触发事件。
-
event
启动触发器的事件,取值范围包括:INSERT、UPDATE、DELETE或TRUNCATE,也可以通过OR同时指定多个触发事件。
-
table_name
触发器对应的表名称。
-
FOR EACH ROW | FOR EACH STATEMENT
触发器的触发频率。
- FOR EACH ROW是指该触发器是受触发事件影响的每一行触发一次。
- FOR EACH STATEMENT是指该触发器是每个SQL语句只触发一次。
未指定时默认值为FOR EACH STATEMENT。约束触发器只能指定为FOR EACH ROW。
-
function_name
用户定义的函数,必须声明为不带参数并返回类型为触发器,在触发器触发时执行。
-
arguments
执行触发器时要提供给函数的可选的以逗号分隔的参数列表。
-
new_trigger_name
修改后的新触发器名称。
42.3 示例
--创建源表及触发表
openGauss=# CREATE TABLE test_trigger_src_tbl(id1 INT, id2 INT, id3 INT);
openGauss=# CREATE TABLE test_trigger_des_tbl(id1 INT, id2 INT, id3 INT);
--创建触发器函数
openGauss=# CREATE OR REPLACE FUNCTION tri_insert_func() RETURNS TRIGGER AS
$$
DECLARE
BEGIN
INSERT INTO test_trigger_des_tbl VALUES(NEW.id1, NEW.id2, NEW.id3);
RETURN NEW;
END
$$ LANGUAGE PLPGSQL;
openGauss=# CREATE OR REPLACE FUNCTION tri_update_func() RETURNS TRIGGER AS
$$
DECLARE
BEGIN
UPDATE test_trigger_des_tbl SET id3 = NEW.id3 WHERE id1=OLD.id1;
RETURN OLD;
END
$$ LANGUAGE PLPGSQL;
openGauss=# CREATE OR REPLACE FUNCTION TRI_DELETE_FUNC() RETURNS TRIGGER AS
$$
DECLARE
BEGIN
DELETE FROM test_trigger_des_tbl WHERE id1=OLD.id1;
RETURN OLD;
END
$$ LANGUAGE PLPGSQL;
--创建INSERT触发器
openGauss=# CREATE TRIGGER insert_trigger
BEFORE INSERT ON test_trigger_src_tbl
FOR EACH ROW
EXECUTE PROCEDURE tri_insert_func();
--创建UPDATE触发器
openGauss=# CREATE TRIGGER update_trigger
AFTER UPDATE ON test_trigger_src_tbl
FOR EACH ROW
EXECUTE PROCEDURE tri_update_func();
--创建DELETE触发器
openGauss=# CREATE TRIGGER delete_trigger
BEFORE DELETE ON test_trigger_src_tbl
FOR EACH ROW
EXECUTE PROCEDURE tri_delete_func();
--执行INSERT触发事件并检查触发结果
openGauss=# INSERT INTO test_trigger_src_tbl VALUES(100,200,300);
openGauss=# SELECT * FROM test_trigger_src_tbl;
openGauss=# SELECT * FROM test_trigger_des_tbl; //查看触发操作是否生效。
--执行UPDATE触发事件并检查触发结果
openGauss=# UPDATE test_trigger_src_tbl SET id3=400 WHERE id1=100;
openGauss=# SELECT * FROM test_trigger_src_tbl;
openGauss=# SELECT * FROM test_trigger_des_tbl; //查看触发操作是否生效
--执行DELETE触发事件并检查触发结果
openGauss=# DELETE FROM test_trigger_src_tbl WHERE id1=100;
openGauss=# SELECT * FROM test_trigger_src_tbl;
openGauss=# SELECT * FROM test_trigger_des_tbl; //查看触发操作是否生效
--修改触发器
openGauss=# ALTER TRIGGER delete_trigger ON test_trigger_src_tbl RENAME TO delete_trigger_renamed;
--删除触发器
openGauss=# DROP TRIGGER insert_trigger ON test_trigger_src_tbl;
openGauss=# DROP TRIGGER update_trigger ON test_trigger_src_tbl;
openGauss=# DROP TRIGGER delete_trigger_renamed ON test_trigger_src_tbl;
标签:src,触发器,42,trigger,tbl,test,openGauss From: https://blog.51cto.com/shuchaoyang/7126769