ABAP DESCRIBE语句
DESCRIBE
DESCRIBE FIELD
DESCRIBE FIELD dobj
[TYPE typ [COMPONENTS com]]
[LENGTH ilen IN {BYTE|CHARACTER} MODE]
[DECIMALS dec]
[OUTPUT-LENGTH olen]
[HELP-ID hlp]
[EDIT MASK mask].
TYPE typ
以下是不同类型的dobj返回的类型ID列表，ID大小写敏感：
|
Numeric Data Type |
ID |
|
b |
b |
|
s |
s |
|
i |
I |
|
p |
P |
|
decfloat16 |
a |
|
decfloat34 |
e |
|
f |
F |
|
Character-Like Data Type |
ID |
|
c |
C |
|
string |
g |
|
n |
N |
|
d |
D |
|
t |
T |
|
Byte-Like Data Type |
ID |
|
x |
X |
|
xstring |
y |
|
Reference Type |
ID |
|
Data reference |
l |
|
Object reference |
r |
|
Complex Type |
ID |
|
Flat structure |
u |
|
Deep structure |
v |
|
Internal table |
h |
COMPONENTS选项是对结构的字段数进行统计，如果有内嵌的结构，则只算直接（最高级别的）内嵌的结构，且只算做１个。
DATA: BEGIN OF struc1,
comp1 TYPE c LENGTH 1,
comp2 TYPE string,
BEGIN OF struc2,
comp1 TYPE c LENGTH 1,
comp2 TYPE i,
END OF struc2,
END OF struc1,
typ1 TYPE c LENGTH 1,
comp1 TYPE i,
typ2 TYPE c LENGTH 1,
comp2 TYPE i.
DESCRIBE FIELD: struc1 TYPE typ1 COMPONENTS comp1,
struc1-struc2 TYPE typ2 COMPONENTS comp2.
WRITE:/ typ1,comp1,/ typ2,comp2.
DESCRIBE FIELD: struc1 TYPE typ1,
struc1-struc2 TYPE typ2.
WRITE:/ typ1,/ typ2.
v 3
u 2
v
u
LENGTH ilen
当使用IN CHARACTER MODE选项时，dobj必须是flat and character-like，针对deep data types的dobj，你只能使用IN BYTE MODE，并且此情况下返回的长度为引用所占长度（在SAP系统中每个reference的长度固定为8 bytes）
对于固定长度类型的dobj，是在创建这个变量时就已决定。如果字符串类型，则不会计算尾部空格，此时可以使用预置函数strlen来测定
DATA: text TYPE c LENGTH 1,
blen TYPE i,
clen TYPE i,
bytes TYPE i.
DESCRIBE FIELD text LENGTH blen IN BYTE MODE.
DESCRIBE FIELD text LENGTH clen IN CHARACTER MODE.
bytes = blen / clen.
WRITE:/ blen,clen,bytes.
2 1 2
DECIMALS dec
dobj的小数位
DATA: p TYPE p LENGTH 8 DECIMALS 4,
i TYPE i.
DESCRIBE FIELD p DECIMALS i.
WRITE:/ i.
4
OUTPUT-LENGTH olen
测试dobj屏幕输出宽度，对于那些固定长度数据类型，输出宽度都是已经预置好的，对于strings，则为0
Numeric Data Types
|
Data Type |
Output length |
|
b |
3 |
|
s |
5 |
|
i |
11 |
|
p |
2 x length of dobj (+ 1, if there is a decimal separator) |
|
decfloat16 |
24 |
|
decfloat34 |
46 |
|
f |
24 |
注：上面表中的s类型显示宽度只有5位，不中以显示符号；i显示宽度为11,可以显示符号
Character-like data types
|
Data Type |
Output Length |
|
c |
Length of dobj, maximum 255 |
|
string text field literals |
根据屏幕列表设置的最大宽度来决定。如果字符不满List设置的宽度时，left-justified输出时会在右边补空格，right-justified输出时会在左边补空格，centered outputs输出时两端补空格 |
|
n |
Length of dobj, maximum 255 |
|
d |
8 |
|
t |
6 |
Byte-Like Data Types
|
Data Type |
Output Length |
|
x |
2 x length of dobj, maximum 255 |
|
xstring |
2 x number of bytes contained |
DATA: date1 TYPE d,
date2 TYPE sy-datum,
olen1 TYPE i,
olen2 TYPE i.
DESCRIBE FIELD date1 OUTPUT-LENGTH olen1.
DESCRIBE FIELD date2 OUTPUT-LENGTH olen2.
WRITE: / date1,date2,/ olen1,olen2.
00000000 00.00.0000
8 10
HELP-ID hlp
DATA: carrid TYPE spfli-carrid,
hlp TYPE string,
struc TYPE dfies-tabname,
comp TYPE dfies-fieldname.
DESCRIBE FIELD carrid HELP-ID hlp.
SPLIT hlp AT '-' INTO struc comp.
WRITE:/ hlp, / struc,/ comp.
CALL FUNCTION 'F4IF_FIELD_VALUE_REQUEST'
EXPORTING
tabname = struc
fieldname = comp.
EDIT MASK mask
If a conversion routine is assigned to the data object dobj by referring to a domain in ABAP Dictionary, two equals signs "==" precede the name of the conversion routine and the result is assigned to the data object mask.
DATA: time TYPE s_fltime,
seconds TYPE i,
msk TYPE string.
DESCRIBE FIELD time EDIT MASK msk.
WRITE msk.
seconds = 333.
WRITE / seconds USING EDIT MASK msk.
==SDURA
5:33
DESCRIBE TABLE
DESCRIBE TABLE itab [KIND knd] [LINES lin] [OCCURS n].
不同的选项使你能够判断表类型、行数、初始化大小。另外，系统字段sy-tfill 和 sy-tleng 保存着表行数量和以字节计的表行长度。注：为了更详细的关于内表的信息，应用RTTS的方法代替语句describe table。没有指定一个附加项，语句describe table 只设置系统字段sy-tfill 和sy-tleng的值。
a) KIND knd
标识为T 时代表标准表，为S时代表排序表，为H时代表哈希表。这些值在类型组SYDES中已被定义成常量sydes_kind-standed ，sydes_kind-sorted，sydes_kind-hashed。
b) LINES lin 内表表行数量
注：在版本6.10中，内表表行的当前数量也可以用内建函数lines来判断
c) OCCURS n
在内表用选项initial size 或者老式的选项ocurs创建期间决定内表所需要的初始化内存大小
FORM sort_descending CHANGING itab TYPE ANY TABLE.
DATA tabkind TYPE c LENGTH 1.
DESCRIBE TABLE itab KIND tabkind.
IF tabkind = sydes_kind-standard OR
tabkind = sydes_kind-hashed.
SORT itab DESCENDING.
ELSEIF tabkind = sydes_kind-sorted.
MESSAGE '...' TYPE 'E'.
ELSE.
MESSAGE '...' TYPE 'E'.
ENDIF.
ENDFORM.
DESCRIBE DISTANCE
DESCRIBE DISTANCE BETWEEN dobj1 AND dobj2 INTO dst
IN {BYTE|CHARACTER} MODE.
dobj1 and dobj2两个变量地址起始位置的距离
DATA: BEGIN OF struc,
comp1 TYPE i,
comp2 TYPE x LENGTH 1,
comp3 TYPE c LENGTH 4 VALUE 'Hey',
comp4 TYPE c LENGTH 4 VALUE 'you!',
comp5 TYPE x,
END OF struc.
DATA: off TYPE i,
len TYPE i,
len2 TYPE i.
FIELD-SYMBOLS: <hex> TYPE x,
<result> TYPE c.
DESCRIBE DISTANCE BETWEEN:
struc AND struc-comp3 INTO off IN BYTE MODE,
struc-comp3 AND struc-comp5 INTO len IN BYTE MODE,
struc AND struc-comp1 INTO len2 IN BYTE MODE.
ASSIGN: struc TO <hex> CASTING,
<hex>+off(len) TO <result> CASTING.
WRITE: / 'Offset off is', off,
/ 'Length len is', len,
/ '<result> points to', <result>,
/ len2.
Offset off is 6
Length len is 16
<result> points toHey you!
0
