如何在Oracle中实现Mariadb中的动态列？

-- 创建包含虚拟列的视图
CREATE OR REPLACE VIEW my_view AS
SELECT id, name, age, salary, (CASE WHEN dynamic_column = 'column1' THEN column1
                                   WHEN dynamic_column = 'column2' THEN column2
                                   ELSE NULL END) AS dynamic_column
FROM my_table;

-- 使用动态SQL生成视图
DECLARE
  sql_stmt VARCHAR2(1000);
BEGIN
  sql_stmt := 'CREATE OR REPLACE VIEW my_view AS SELECT id, name, age, salary';
  
  -- 根据需要添加或删除列
  IF condition THEN
    sql_stmt := sql_stmt || ', column1 AS dynamic_column';
  END IF;
  
  sql_stmt := sql_stmt || ' FROM my_table';
  
  EXECUTE IMMEDIATE sql_stmt;
END;

-- 使用触发器更新虚拟列
CREATE OR REPLACE TRIGGER my_trigger
BEFORE INSERT OR UPDATE OR DELETE ON my_table
FOR EACH ROW
BEGIN
  -- 更新虚拟列的值
  :NEW.dynamic_column := CASE WHEN :NEW.dynamic_column = 'column1' THEN :NEW.column1
                             WHEN :NEW.dynamic_column = 'column2' THEN :NEW.column2
                             ELSE NULL END;
END;

-- 查询视图
SELECT * FROM my_view;