ALV report flow diagram

https://zhuanlan.zhihu.com/p/355316708

Write a ALV The steps of the report are as follows ：
1. Declare the variables needed

TABLES: mseg , mkpf  , ztmm063h ,  mara , makt , ekpo , ekko ,ztbc120h.

2. Define various options for the screen ：

for example

SELECT-OPTIONS :	 s_mblnr FOR mseg-mblnr,
									 s_budat FOR mkpf-budat,
									 s_werks FOR mseg-werks,
									 s_lgort FOR mseg-lgort,
									 s_matnr FOR mara-mathn,
									 s_charg FOR ztmm063h-charg,
									 s_ebeln FOR ekpo-ebeln,
									 s_lifnr FOR mseg-lifnr.
SELECT-OPTIONS END OF BLOCK b1.	 

3. Reference output structure

DATA: gt_alv TYPE TABLE OF zsmm141a_alv,
			gwa_alv TYPE zsmm141a_alv.

4. Define data processing logic

START-OF-SELECTION.
	PERFORM frm_get_data.

Related knowledge

Internal table

An internal table is a sequence of data objects of the same type .
The internal table only exists during the operation of the program .

1. Purpose of internal table ：
Temporarily store the data read from the database table , For further processing
Temporarily store the list data for display
As a data buffer, it is used for data exchange with other programs

2. Characteristics of internal tables
The number of rows in the internal table is not predefined , But dynamic growth （ Every time I grow 8K）
Row type of internal table （LINETYPE） It can be any kind of ABAP data type .

3. Types of internal tables ：
Standard table , There is a linear index , Access mainly through index .
Sort table , Defined primary key , It can be accessed through primary key and index .
Hashtable , No index , It can only be accessed through the primary key .

4. Processing keywords of internal tables
APPEND： Add the contents of the workspace to the end of the internal table
INSERT: Add the contents of the workspace to the location specified by the internal table （ Line number ）
COLLECT: Compare non numeric fields , Add numeric fields to the internal table
MODIFY: Overwrite the contents of the workspace with the rows specified in the internal table
DELECT: Delete the specified row from the internal table
LOOP AT: Read the data of the internal table row by row into the workspace
READ TABLE: Read the data of a specific row of the internal table into the workspace
SORT： Sort the interior
CLEAR: Be clear about the contents of the workspace
REFRESH： Delete all records in the internal table

database

stay ABAP In the program , There are two ways to access the database

OPEN SQL ： standard SQL Subset , And ABAP Fully integrated , It is database independent , The database interface will automatically convert it to the standard of the database used SQL.

NATIVE SQL： Related to databases , Use the standards provided by the database SQL, Without syntax checking and conversion of database interface .

Avoid using NATIVE SQL

OPENSQL Visit introduction

OPENSQL Only function data operation language DML, Data definition language DDL adopt ABAP Dictionary object control .

adopt OPEN SQL What can be done ：SELECT , UPDATE , INSERT , DELETE , MODIFY

You can use the system variable SY-SUBRC Judge whether the operation is successful ,SY-SUBRC = 0 Indicates successful execution , SYBRC <>0 It means that the execution is unsuccessful ,
For more detailed information, refer to the online help document

SAP SQL The basic format

SELECT Clause is used to determine what data to read - What fields does the result contain - Need to read single record or multiple records （SINGLE）- Whether the result can contain duplicate records （DISTINCT）

INTO Clause indicates the declared location where the read data is put into memory （ Variable , work area , Internal table ）FROM Clause represents the data source （ Tables or views ）

SAP SQL Read mode

have access to SELECT SINGLE Read a single record , Make sure that the records read out are unique , Need to be in WHERE Determine all primary keys in the statement

If not applicable SINGLE keyword , Then read all that meet WHERE Record of conditions , There are two ways to read ：

1. Read the target area line by line in a circular way , Need by ENDSELECT Statement with .

2. Use SELECT…INTO TABLE sentence , Read all records that meet the conditions into the internal table at one time , No loops are used , Step needs ENDSELECT. This way of reading data is more efficient than the previous one .

3. stay INO clause , have access to CORRENPSONDING FIELDS OF , The system only fills in fields with the same name , If not applicable , Fill in from left to right

4. In the field list and WHERE clause , Just specify the field name , There is no need to specify the table name .•WHERE You can use AND or OR Realize complex logical conditions .

5.SELECT * Statement to read all fields of the transparent table , There can be no INTO Clause , But you have to use TABLES Declare transparent table .

SAP SQL Table linking method

have access to JOIN Connect multiple transparent tags to query
INNER JOIN
LEFT OUTER JOIN
RIGHT OUTER JOIN
Transparent tables can use aliases .
If the field exists in only one table , There is no need to specify the table name