学生成绩管理数据库触发器示例：自动更新学分、删除和更新选课记录

(1) 创建触发器tri_ins_xscj：

CREATE TRIGGER tri_ins_xscj
AFTER INSERT ON xscj
FOR EACH ROW
UPDATE xsqk SET zxf = zxf + NEW.xf WHERE xh = NEW.xh;

(2) 创建触发器tri_delete_xskc：

CREATE TRIGGER tri_delete_xskc
AFTER DELETE ON xskc
FOR EACH ROW
DELETE FROM xscj WHERE kch = OLD.kch;

(3) 创建触发器tri_update_xskc：

CREATE TRIGGER tri_update_xskc
AFTER UPDATE ON xskc
FOR EACH ROW
UPDATE xscj SET kch = NEW.kch WHERE kch = OLD.kch;