2019.12.05【ABAP随笔】 分组循环(LOOP AT Group) / REDUCE

ABAP 7.40新语法 LOOP AT Group 和 REDUCE

 1 *LOOP AT itab result [cond] GROUP BY key ( key1 = dobj1 key2 = dobj2 …
 2 *      [gs = GROUP SIZE] [gi = GROUP INDEX] )
 3 *      [ASCENDING|DESCENDING [AS TEXT]]
 4 *      [WITHOUT MEMBERS]
 5 *      [{INTO group}|{ASSIGNING }]
 6 *      …
 7 *      [LOOP AT GROUP group|
 8 *      …
 9 *      ENDLOOP.]
10 *      …
11 *ENDLOOP.
12 *
13 *… REDUCE type(
14 *INIT result = start_value
15 *           …
16 *FOR for_exp1
17 *FOR for_exp2
18 *…
19 *NEXT …
20 *           result = iterated_value
21 *… )
22 
23 
24 "首先创建一个内表
25 TYPES:BEGIN OF ty_data,
26         id       TYPE i, "人员ID
27         name     TYPE char10, "人员名称
28         country  TYPE char10, "国家
29         language TYPE char2, "语言
30         age      TYPE i,
31       END OF ty_data,
32       ty_t_data TYPE STANDARD TABLE OF ty_data WITH EMPTY KEY.
33 
34 "数据
35 DATA(gt_data) = VALUE ty_t_data(
36 ( id = 1 name = 'Jerry' country = 'China' language = 'ZH' age = 18 )
37 ( id = 2 name = 'Jack' country = 'China' language = 'ZH' age = 19 )
38 ( id = 3 name = 'Nick' country = 'Korea' language = 'EN' age = 20 )
39 ( id = 4 name = 'Rossi' country = 'Korea' language = 'EN' age = 25 )
40 ( id = 5 name = 'Randy' country = 'Korea' language = 'EN' age = 23 )
41 ( id = 6 name = 'Tab' country = 'China' language = 'ZH' age = 22 )
42 ( id = 7 name = 'Lily' country = 'Korea' language = 'EN' age = 21 )
43 ( id = 8 name = 'Lucy' country = 'China' language = 'EN' age = 24 )
44 ( id = 9 name = 'Zera' country = 'China' language = 'EN' age = 28 )
45 ( id = 10 name = 'Grace' country = 'China' language = 'EN' age = 19 )
46 )
47 .
48 
49 "REDUCE
50 "1计算年龄最大
51 DATA(lv_age_max_zh) = REDUCE i( INIT x = 0 FOR lw_data IN gt_data
52                       WHERE ( language = 'ZH' ) NEXT x = nmax( val1 = x
53                                                                val2 = lw_data-age )
54                                                                ) .
55 WRITE:/ |说中文的人中年龄最大的是：{ lv_age_max_zh  } |.
56 
57 "2.输出的reduce
58 TYPES:outref TYPE REF TO if_demo_output.
59 DATA(output) = REDUCE outref( INIT out = cl_demo_output=>new( )
60                               text = 'Count up：'
61                               FOR n = 1 UNTIL n > 11
62                               NEXT out = out->write( text )
63                               text = | { n } | ).
64 output->display( ).
65 
66 "分组循环
67 "1.ls_data这个工作区里面是没有内容的
68 "2.里面只有size index 和分组参数
69 LOOP AT gt_data INTO DATA(ls_data) GROUP BY ( country = ls_data-country language = ls_data-language
70   size = GROUP SIZE index = GROUP INDEX ) ASCENDING ASSIGNING FIELD-SYMBOL().
71 
72   WRITE:/ |Group:{ -index } Country :{ -country } language : { -language }| &
73   | Number lines :{ -size } |.
74 
75   "3.按照中的分组参数循环 GT_data中的数据
76   LOOP AT GROUP  ASSIGNING FIELD-SYMBOL().
77 
78     WRITE:/ | Name:{ -name } |.
79 
80   ENDLOOP.
81 
82   DATA(lv_age_max) = REDUCE i( INIT max = 0 FOR lw_member IN GROUP 
83                              NEXT max = nmax( val1 = max val2 = lw_member-age ) ).
84 
85   DATA(lv_age_min) = REDUCE i( INIT min = 100 FOR lw_member IN GROUP 
86                                NEXT min = nmin( val1 = min val2 = lw_member-age ) ).
87 
88   DATA(lv_age_sum) = REDUCE i( INIT sum = 0 FOR lw_member IN GROUP 
89                                NEXT sum = sum + lw_member-age ).
90   DATA(lv_age_avg) = lv_age_sum / -size.
91 
92   WRITE:/ | 该组最大年龄，最小年龄和平均年龄分别为:{ lv_age_max } { lv_age_min } { lv_age_avg } |.
93 ENDLOOP.

结果为:

个人感觉LOOP AT GROUP 和 REDUCE可以很好的代替 LOOP 中使用 AT END OF field 和 AT NEW field ( 这个是需要调整内表结构字段顺序的)。

平时用在分组求和，分组操作的时候还是很好用的。

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