ABAP READ内表新老语法对比
1、读取内表行新语法
740新语法中，对标READ，提出了新的语法，如下：
1.1、根据字段值查找
"-----------------------------@斌将军----------------------------- "老语法 READ TABLE lt_acd INTO ls_acd WITH KEY rbukrs = gs_acd-rbukrs. IF sy-subrc EQ 0. ENDIF. "新语法 ls_acd = lt_acd[ rbukrs = gs_acd-rbukrs ]. "-----------------------------@斌将军-----------------------------
1.2、按索引查找
"-----------------------------@斌将军----------------------------- "老语法 READ TABLE lt_acd INTO ls_acd INDEX 1. IF sy-subrc EQ 0. ENDIF. "新语法 ls_acd = lt_acd[ 1 ]. "-----------------------------@斌将军-----------------------------
1.3、判断记录是否存在
"-----------------------------@斌将军----------------------------- "老语法 READ TABLE lt_acd WITH KEY rbukrs = gs_acd-rbukrs TRANSPORTING NO FIELDS. IF sy-subrc EQ 0. ENDIF. "新语法 IF LINE_EXISTS( lt_acd[ rbukrs = gs_acd-rbukrs ] ). ENDIF. "-----------------------------@斌将军-----------------------------
1.4、获取行索引
"-----------------------------@斌将军----------------------------- "老语法 READ TABLE lt_acd WITH KEY rbukrs = gs_acd-rbukrs TRANSPORTING NO FIELDS. IF sy-subrc EQ 0. WRITE:SY-TABIX. ENDIF. "新语法 LV_INDEX = LINE_INDEX( lt_acd[ rbukrs = gs_acd-rbukrs ] ). "-----------------------------@斌将军-----------------------------
需要特别注意的是，新语法必须用TRY CATCH，或在查询前，用LINE_EXISTS()判断是否存在，否则将会导致DUMP
TRY . ls_acd = lt_acd[ rbukrs = '333' ]. CATCH cx_sy_itab_line_not_found . MESSAGE '未找到数据' TYPE 'E' . ENDTRY. "或 IF line_exists( lt_acd[ rbukrs = '333' ] ). ls_acd = lt_acd[ rbukrs = '333' ]. ELSE. MESSAGE '未找到数据' TYPE 'E' . ENDIF.
2.效率对比
由于老语法可以使用二分法查找，因此在效率上将会有差异。
现编写一个实例，循环2万条数据GT_ACD，并循环查询有14万条数据的LT_ACD中对应的值。下边测试各种情况下的查询速度
2.1、新语法
"-----------------------------@斌将军----------------------------- "1.测试新语法------------------------------------ GET TIME STAMP FIELD lv_current1. CLEAR:lv_index. LOOP AT gt_acd INTO gs_acd. lv_index = lv_index + 1. TRY . ls_acd = lt_acd[ rbukrs = gs_acd-rbukrs gjahr = gs_acd-gjahr belnr = gs_acd-belnr docln = gs_acd-docln ]. CATCH cx_sy_itab_line_not_found . MESSAGE '未找到数据' TYPE 'E' . ENDTRY. ENDLOOP. GET TIME STAMP FIELD lv_current2. "-----------------------------@斌将军-----------------------------
结果：
2.2、老语法READ
"-----------------------------@斌将军----------------------------- "2.测试老语法------------------------------------ GET TIME STAMP FIELD lv_current1. CLEAR:lv_index. LOOP AT gt_acd INTO gs_acd. lv_index = lv_index + 1. READ TABLE lt_acd INTO ls_acd WITH KEY rbukrs = gs_acd-rbukrs gjahr = gs_acd-gjahr belnr = gs_acd-belnr docln = gs_acd-docln. IF sy-subrc EQ 0. ENDIF. ENDLOOP. GET TIME STAMP FIELD lv_current2. "-----------------------------@斌将军-----------------------------
结果：
2.3、老语法READ二分查找
"-----------------------------@斌将军----------------------------- GET TIME STAMP FIELD lv_current1. CLEAR:lv_index. SORT lt_acd BY rbukrs gjahr belnr docln. LOOP AT gt_acd INTO gs_acd. READ TABLE lt_acd INTO ls_acd WITH KEY rbukrs = gs_acd-rbukrs gjahr = gs_acd-gjahr belnr = gs_acd-belnr docln = gs_acd-docln BINARY SEARCH. IF sy-subrc EQ 0. lv_index = lv_index + 1. ENDIF. ENDLOOP. GET TIME STAMP FIELD lv_current2. "-----------------------------@斌将军-----------------------------
结果：< 1S
2.4、新语法+排序表
"-----------------------------@斌将军----------------------------- "4.测试新语法+排序表------------------------------------ lt_acd_sort = lt_acd. GET TIME STAMP FIELD lv_current1. CLEAR:lv_index. LOOP AT gt_acd INTO gs_acd. lv_index = lv_index + 1. TRY . ls_acd = lt_acd_sort[ rbukrs = gs_acd-rbukrs gjahr = gs_acd-gjahr belnr = gs_acd-belnr docln = gs_acd-docln ]. CATCH cx_sy_itab_line_not_found . MESSAGE '未找到数据' TYPE 'E' . ENDTRY. ENDLOOP. GET TIME STAMP FIELD lv_current2. "-----------------------------@斌将军-----------------------------
结果：< 1S
综上所述：不使用二分查找，则新老语法都很慢。使用二分查找或新语法搭配排序表，则速度都有非常明显的提升