oracle转mysql，float怎么不指定精度啊

oracle中float()定义浮点型，不指定精度的。但是在mysql float(M,D)一定要指定精度才能保存，请问怎么才能不指定精度呢
顺便问下，oracle中的延迟约束和触发器在mysql中怎么写呢
oracle中的延迟约束：
ALTER TABLE "WMSUSER"."T_HIGHWIND" ADD CONSTRAINT "SYS_C0011098" CHECK ("ID" IS NOT NULL) NOT DEFERRABLE INITIALLY IMMEDIATE NORELY VALIDATE;
oracle中的触发器
CREATE TRIGGER "WMSUSER"."HIGHWIND_INCREMENT" BEFORE INSERT ON "WMSUSER"."T_HIGHWIND" REFERENCING OLD AS "OLD" NEW AS "NEW" FOR EACH ROW
BEGIN
select HIGHWIND_SEQ.nextval into :new.ID from dual;
END;

你指定float(20,6)就行了，设置个足够大的精度。