ABAP如何从数据表中取描述

背景： 如果我们要从多个表取数据到一个内表中，则可能有两种方法，1种是可以outer join直接修改内表，另外一种则可以是用循环，下面是两个例子。

以下是left outer join的用法

 SELECT T1~ZDZNY AS A1,   T1~BUKRS AS A2,  T1~WERKS AS A3, T1~EKORG AS A4,  T1~LIFNR AS A5,  T1~MATNR AS A6,   T1~MEINS AS A7,   T1~QCSL AS A8,  T1~HGSL AS A9,  T1~THSL AS A10,
     T1~KPSL AS A11,  T1~JCSL AS A12, T1~BHSL AS A13, T1~ZBEIZ AS A14, T1~ERDAT AS A15, T1~ERNAM AS A16 , T1~UZEIT AS A17,T2~MAKTX AS A18, T3~NAME1 AS A19
     FROM ZSRMDZD as t1
     left outer join  LFA1 as t3  on t3~LIFNR = t1~LIFNR
    left outer join  makt as t2  on t2~MATNR = t1~MATNR
     INTO TABLE @ITEM
   WHERE T1~ZDZNY IN @S_ZDZNY
   AND T1~BUKRS  IN  @S_BUKRS
   AND T1~WERKS IN  @S_WERKS
   AND T1~EKORG IN  @S_EKORG
    AND T1~LIFNR IN  @S_LIFNR
    AND T1~MATNR IN   @S_MATNR.

以下是循环来取字段
for all entri in + read table