# SAP ABAP Memo

###### tags: `SAP` `ABAP`

[A Very Good Reference(in Japanese)](https://it-biz.online/sap/abap-abc/#toc4)

[技術總結 之後再來看](https://www.cnblogs.com/jiangzhengjun/p/7264657.html#_Toc410466841)

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## Data & Types

* Syntax: 一定要先宣告

TYPES type_name TYPE data_type

DATA variable_name TYPE vaiable_TYPE.

e.g. DATA EMPLOYEE_NUMBER TYPE I.

* 口訣：**types聲明類型，data聲明變數，變數要有類型**

* Data Types
DTIF固定長度
其餘不固定

另，可以利用TYPES語法創造非SAP Dictionary提供的data type
例如：

* 這是一個長度為15的char類型名為text1

TYPES text1(15) TYPE C.

DATA var TYPE text1.

* 這是一個名為t_staff的表狀data

TYPES: BEGIN OF t_staff,
       no(3) TYPE N,
       name(20) TYPE String,
       END OF t_staff.

* 設定一個變數staff其資料類型為t_staff       
DATA staff TYPE t_staff.

* Processing Data
賦值：
a = 16. / MOVE 16 TO a. / WRITE a TO b.
用第一種即可

計算：
(COMPUTE) b = a * 100.

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## 流程控制

* if... else if...else

IF 條件.
   do something.

ELSEIF 條件.
   do something.

ELSE.
   do something.

ENDIF.       

ELSEIF & ELSE are not mandatory, but **ENDIF is**.
* while loop

WHILE 條件.

do something.

ENDWHILE.

* 邏輯運算子
不等於為<>
其餘都一樣

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## System Variables
* Frequently Used System Variable

* SY-SUBRC (similar to Boolean but the type is integer)
RC stands for Return Code
SY-SUBRC = 0 -> success
SY-SUBRC = 4 -> failure
SY-SUBRC = 8 -> special type of failure
通常的寫法為 "判斷SY-SUBRC=0 or SY-SUBRC<>0" 即可

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## Data Dictionary
* 作用：創建與管理Data

* Domain, Data Element, Table
Domain定義Data Element的屬性(例如type, length等等)
Data Element組成Table