CREATE OR REPLACE TRIGGER "TIG_M_BOM_COMPONENT_IUD" 
AFTER INSERT OR DELETE OR UPDATE ON M_BOM_COMPONENT
FOR EACH ROW
declare
    o_existitem           number; 
BEGIN
    case
        when inserting then
            --执行插入时的操作
        when updating then
            --执行更新时的操作
        when deleting then
            --执行删除时的操作
    end case;
END;