SAP ABAP开发学习——代码优化

1.SELECT/ENDSELECT

首先用*取全部字段，比给定字段取数效率低

其次通过字段取数，给两个关键字要比只给一个效率高

' = '放在 ‘ in '选择界面的前面

2.READ

TRANSPORTING NO FIELDSZ只读取，不赋值，为了确定是否读取成功，就要使用SY-SUBRC

先排序，形成索引表，在二分法读取

使用field_symbols效率高

3.LOOP+SELECT

FOR ALL ENTRIES IN 读多条，可以让MAKT表取数时只取符合条件且内表GT_MARA中已经有的条目，可以避免全部数据取一遍，减少时间

4.判断某个字段的值，CASE语句比IF语句好。如果是多个不确定的条件，再使用IF判断

5.关于清空操作

依次读取，每次都会进行覆盖，所以不需要清空语句

只读一条，如果此时没有第二十条，工作区内是其原来的数据，所以需要提前清空

MAKT中没有MEINS字段，move-corresponding只会把相匹配字段值赋过去，其他的字段保持原来的值，这中间不应该加清空。

MAKT中没有MEINS字段，这种如果每次不需要保留上一行的MEINS值，就需要加上清空

6.LOOP+LOOP

对内层要读的表排序，实现数据分成小块，减少读取次数。

7.对四个表取数

GT_T134T

MATNR  SPRAS  MTBEZ

FORM get_data.
  DATA: BEGIN OF lt_mard OCCURS 0,
          werks TYPE mard-werks,
          lgort TYPE mard-lgort,
          matnr TYPE mard-matnr,
          labst TYPE mard-labst,
        END OF lt_mard.

  DATA: BEGIN OF lt_mara OCCURS 0,
          matnr TYPE mara-matnr,
          mtart TYPE mara-mtart,
          meins TYPE mara-meins,
        END OF lt_mara.

  DATA: BEGIN OF lt_makt OCCURS 0,
          matnr TYPE makt-matnr,
          spras TYPE makt-spras,
          maktx TYPE makt-maktx,
        END OF lt_makt.

  DATA: BEGIN OF lt_t134t OCCURS 0,
          mtart TYPE t134t-mtart,
          spras TYPE t134t-spras,
          mtbez TYPE t134t-mtbez,
        END OF lt_t134t.

*  取基本表
  SELECT *
    FROM mard
    INTO CORRESPONDING FIELDS OF TABLE lt_mard
    WHERE werks IN s_werks
    AND lgort IN s_lgort
    AND matnr IN s_matnr.

  CHECK lt_mard IS NOT INITIAL.
* 取MARA
  SELECT *
    FROM mara
    INTO CORRESPONDING FIELDS OF TABLE lt_mara
    FOR ALL ENTRIES IN lt_mard
    WHERE matnr = lt_mard-matnr
    AND mtart IN s_mtart.
  SORT lt_mara BY matnr.

* 取MAKT
  SELECT *
    FROM makt
    INTO CORRESPONDING FIELDS OF TABLE lt_makt
    FOR ALL ENTRIES IN lt_mard
    WHERE matnr = lt_mard-matnr.
  SORT lt_makt BY matnr.

* 取T134T
  SELECT *
    FROM t134t
    INTO CORRESPONDING FIELDS OF TABLE lt_t134t
    FOR ALL ENTRIES IN lt_mara
    WHERE mtart = lt_mara-mtart.
  SORT lt_t134t BY mtart.

* 循环MARD
  LOOP AT lt_mard.
    MOVE-CORRESPONDING lt_mard TO gs_total.

* 读取MARA
    READ TABLE lt_mara WITH KEY matnr = lt_mard-matnr
                                    BINARY SEARCH.
    IF sy-subrc = 0.
      "赋值.
      gs_total-matnr = lt_mara-mtart.
      gs_total-meins = lt_mara-meins.

    ELSE.
      "退出当前循环
      CONTINUE.
    ENDIF.
* 读MAKT
    READ TABLE lt_makt WITH KEY matnr = lt_mard-matnr
                                        BINARY SEARCH.
    IF sy-subrc = 0.
      "赋值.
      gs_total-spras = lt_mara-spras.
      gs_total-maktx = lt_mara-maktx.
    ENDIF.

* 读T134T
    READ TABLE lt_t134t WITH KEY mtart = lt_mard-mtart
                                        BINARY SEARCH.
    IF sy-subrc = 0.
      "赋值.
      gs_total-mtbez = lt_mara-mtbez.
    ENDIF.

* 赋给TOTAL
    APPEND gs_total TO lt_total.

  ENDLOOP.

ENDFORM.