一応はっとく
^(?:(A)=(\d+)|(B)=(\d+)|(C)=(\d+)|(D)=(\d+)|[^?&]+|[?&])+$⇒$1$2$3$4$5$6$7$8
?A=123&C=456&B=0&A=2222&F=0000&DUMMY⇒A2222B0C456