[转载]SAP ABAP Internal Table 一些事

[转载]SAP ABAP Internal Table 一些事

 

原文地址：SAP ABAP Internal Table 一些事作者：SAP立志

一. Internal Table 的宣告
ABAP/4中的Internal Table是一种Data Structure,类似于其它语言中的STRUTURE,它可以由几个不同类型的字段(field)组成,用来表示具有不同属性的某一事物,单独一笔数据表示某个事物,多笔数据表示具有相同属性的多个事物.例如:
为了存取或记录某班的同学资料,我们创建如下的internal table:
DATA: BEGIN OF STUDENT OCCURS 20,
               STD_ID     TYPE N,
               NAME(10) TYPE C,
               AGE        TYPE I,
               BIRTH      TYPE D,
               SCORE      TYPE P DECIMALS 2,
        END OF STUDENT.
此时我们已经创建了名叫STUDENT的internal table,并且为它预先申请了能够存放20笔资料的Buffer(当然,如果存取资料不止20笔,程序执行时,会自动申请系统Buffer)
Internal table 的定义有以下几种格式:
格式一.     DATA: BEGIN OF <internal table>    OCCURS    <n>,
                     <field 1>    TYPE <type1>,
                    [<field 2>    TYPE <type 2>,
                     <field 3>    TYPE <type 3>,
                      …                    ]
                  END OF    <internal table>.
格式二.     TYPES: BEGIN OF <work area>,
                       <field 1>    TYPE <type1>,
                      [<field 2>    TYPE <type 2>,
                       <field 3>    TYPE <type 3>,
                      …                    ]
                   END OF <work area>.
            TYPES <internal table> TYPE <work area> OCCURS <n>.
格式三.      DATA: BEGIN OF <work area>.
                         INCLUDE STRUCTURE <table name>.
            DATA: END OF <work area>.
            DATA: <internal table> LIKE <work area> OCCURS <n>.
二. APPEND LINE
格式: APPEND [<work area>    TO ] <internal table>.
举例一. (使用work area)
DATA: BEGIN OF LINE,
               COL1 TYPE I,
               COL2 TYPE I,
        END OF LINE.
DATA    ITAB LIKE LINE OCCURS 10.
DO 2 TIMES.
       LINE-COL1 = SY-INDEX.
       LINE-COL2 = SY-INDEX ** 2.
       APPEND LINE TO ITAB.
ENDDO.
LOOP AT ITAB INTO LINE.
        WRITE: / LINE-COL1, LINE-COL2.
ENDLOOP.
执行结果为:
1 1
2 4
举例二. (不使用work area)
          DATA: BEGIN OF ITAB OCCURS 10,
                       COL1 TYPE I,
                       COL2 TYPE I,
                END OF ITAB.
          DO 2 TIMES.
              ITAB-COL1 = SY-INDEX.
              ITAB-COL2 = SY-INDEX ** 2.
              APPEND ITAB.
          ENDDO.
          LOOP AT ITAB.
              WRITE: / ITAB-COL1, ITAB-COL2.
          ENDLOOP.
          执行结果与举例一相同.
举例三. (加入另一个Internal table的元素)
         格式: APPEND LINES OF <itab1> [FROM <n1> ] [TO <n2>] TO <itab2>.
         将<itab1>的元素加入至<itab2>中,可选取自<n1>至<n2>的范围.
         APPEND LINES OF ITAB TO JTAB.
三. COLLECT LINE
COLLECT 指令也是将元素加入Internal table中,与APPEND 的区别是: COLLECT指令在非数值字段相同的情况下,将数值字段汇总.
格式:    COLLECT [<work area> INTO ] <itab>
DATA: BEGIN OF ITAB OCCURS 3,
               COL1(3)    TYPE C,
               COL2       TYPE I,
         END OF ITAB.
         ITAB-COL1 = ‘ABC’.      ITAB-COL2 = 10.
         COLLECT    ITAB.
         ITAB-COL1 = ‘XYZ’.      ITAB-COL2 = 20.
         COLLECT    ITAB.
         ITAB-COL1 = ‘ABC’.      ITAB-COL2 = 80.
         COLLECT    ITAB.
此时, internal table中放的是2笔数据, 分别为:
         ITAB-COL1          ITAB-COL2
          ‘ABC’                 90
          ‘XYZ’                 20
四. INSERT LINE
将元素插入在指定的internal table位置之前.
格式: INSERT [<wa> INTO] [INITIAL LINE INTO ] <itab> [INDEX <idx>]
或者: INSERT LINES OF <itab1> [FROM <n1> TO <n2>] INTO <itab2> INDEX <idx>
其中: <wa>即work area,工作区中的元素.
[INITIAL LINE INTO] :插入一笔初始化的记录.
<itab>: internal table
[INDEX <idx>]: internal table 的记录号.(新加入的元素放在此记录前面)
五. 读取internal table
格式一:
LOOP AT <itab> [INTO <wa>][FROM <n1> TO <n2>][WHERE <conditions>]
         <statement>
ENDLOOP.
格式二:
READ TABLE <itab> [INTO <wa>] [INDEX <idx> / WITH KEY <conditions>]
举例. (格式二)
DATA: BEGIN OF ITAB OCCURS 10,
               COL1 TYPE I,
               COL2 TYPE I,
        END OF ITAB.
        DO 10 TIMES.
            ITAB-COL1 = SY-INDEX.
            ITAB-COL2 = SY-INDEX * 2.
            APPEND ITAB.
ENDDO.
READ TABLE ITAB INDEX 3.
(或者: READ TABLE    ITAB WITH KEY COL1 = 3.)
WRITE: / ‘ITAB-COL1 = ‘, ITAB-COL1, ‘ITAB-COL2 = ‘, ITAB-COL2.
执行结果同样是:
ITAB-COL1 =        3
ITAB-COL2 =        6.
六. 修改internal table 中的值
格式: MODIFY <itab> [FROM <wa>][INDEX <idx>][TRANSPORTING <f1><f2>…][WHERE <conditions>]
举例一. READ TABLE ITAB INDEX 3.
         LINE-COL1 = 29.
         MODIFY ITAB FROM LINE TRANSPORTING COL1.
         将第三笔记录的COL1字段的值修改为29.
举例二. T_SALARY – salary = 50.
         MODIFY T_SALARY TRANSPORTING salary WHERE birthday = ‘1999/12/06’.
七. DELETE internal table中的字段
格式: DELETE <itab> INDEX <idx>.
或:     DELETE <itab>[FROM <n1> TO <n2>] [WHERE <conditions>]
八. Internal table 排序  
SORT <itab> [<order way>][BY <f1><f2>…]
其中:<order way> 有DESCENDING 和ASCENDING, Default 为ASCENDING.
       <f1>: 为指定排序的字段.
九. 加总
SUM.
总和计算存放与work area中,但只能在LOOP 中使用.
例: LOOP AT ITAB INTO LINE.
           SUM.
     ENDLOOP.
     WRITE: / LINE-COL1, LINE-COL2.
十. 初始化internal table
REFRESH <itab>.    清空<itab>中的值.
CLEAR     <itab>.    清空<itab>的Header Line.
FREE       <itab>.    释放记忆体空间.