itab like STANDARD TABLE OF line with KEY table-line.在下面程序中这

itab like STANDARD TABLE OF line with KEY table_line.在下面程序中这段话为什么like不能换成type.
DATA :BEGIN OF line,
num TYPE i,
sqr TYPE i,
END OF line,
itab like STANDARD TABLE OF line with KEY TABLE_LINE.
DO 5 TIMES.
line-num = sy-index.
line-sqr = sy-index ** 2.
APPEND line to itab.
ENDDO.
LOOP AT itab INTO line.
write:/ line-num,line-sqr.
ENDLOOP.
CLEAR itab.