SAP Certification Notes C_TAW12_71 Part-II

SQL STATEMENT INCLUDING UPDATE STRATEGIES

Open SQL & Native SQL

Whenever a transparent table is activated in the ABAP dictionary, a table of the same name is automatically created within the database.

The key field in table is also called the primary key.

Every relational database system has its own native SQL, which is unfortunately database-specific.
Open SQL is database-independent SQL standard for ABAP.

All Open SQL statements fill the following two system fields with return codes:

• SY-SUBRC
  After every Open SQL statement, the system field SY-SUBRC contains 0 if the operation was successful, a value other than 0 if not.
• SY-DBCNT
  After an OPEN SQL statement, the system field SY-DBCNT contains the number of database lines processed.

Open SQL contains the following keywords:

• SELECT - Reads data from database tables.
• INSERT - Adds lines to database tables.
• UPDATE - Changes the contents of lines of database tables.
• MODIFY - Inserts lines into database tables or changes the contents of existing lines.
• DELETE - Delete lines from database tables.
• OPEN CURSOR, FETCH, CLOSE CURSOR - Reads lines of database tables using the cursor.

Open SQL statement do not perform any authorization checks automatically.
You must execute this explicitly in your program.

A SELECT statement is a loop. Except SELECT SINGLE & using the addition INTO TABLE or APPENDING TABLE.

It is important to remember that you cannot specify a client MANDT in the WHERE clause unless you provide the addition CLIENT SPECIFIED
SELECT * FROM mara CLIENT SPECIFIED into TABLE  itab WHERE mandt = 110 .

There are two ways of causing a database rollback.

1. Sending a termination dialog message ( a message with type A)
different message type: A(abend), E(error), I(Information), S(Status), W(Warning),X(Exit).
The transmission of an A type message cause a database rollback and terminates the programme.

2. Using the ABAP statement ROLLBACK WORK
This statement ROLLBACK WORK cause a database rollback but does not terminate the programme.

LOGICAL UNIT OF WORKS

With LUW changes are carried out together or not made at all.

When we use ABAP statement ROLLBACK WORK or COMMIT WORK, you explicitly implement a database rollback or database commit.

LOCK OBJECT
We maintain lock object in the ABAP dictionary . 

The customer name space for lock object is EZ or EY.

When LOCK object is successfully activated the system generate 2 function module.

DEQUEUE_EZDEMO

CALL FUNCTION 'DEQUEUE_EZASD'
* EXPORTING
*   MODE_MARA       = 'S'
*   MANDT           = SY-MANDT
*   MATNR           =
*   X_MATNR         = ' '
*   _SCOPE          = '3'
*   _SYNCHRON       = ' '
*   _COLLECT        = ' '
ENQUEUE_EZDEM

CALL FUNCTION 'ENQUEUE_EZASD'
* EXPORTING
*   MODE_MARA            = 'S'
*   MANDT                = SY-MANDT
*   MATNR                =
*   X_MATNR              = ' '
*   _SCOPE               = '2'
*   _WAIT                = ' '
*   _COLLECT             = ' '
* EXCEPTIONS
*   FOREIGN_LOCK         = 1
*   SYSTEM_FAILURE       = 2
*   OTHERS               = 3
          .
IF sy-subrc <> 0.
* MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
*         WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.

The lock module created by the system automatically contains input parameters for the lock parameters.
The lock module consists of the key fields of the primary table.

The lock module ENQUEUE produces an exception if the lock cannot be obtained.
Unlike ENQUEUE functional module, the DEQUEUE functional module do not trigger any exceptions

If you want to release all locks, you can use the functional module DEQUEUE_ALL.

If client is not provided when the ENQUEUE function is called, the lock only applies to the current execution client
If client is specified the  lock only applies to that client.
If client is specified as space, the lock applies to all clients.

We can override the default lock module in the lock object by using the parameter MODE_.

The parameter X_ allows u to lock record that contains an initial value in the corresponding parameter.

The parameter _SCOPE defines the validity area of the lock.

The parameter _WAIT defines whether the lock request should be repeated if the first lock attempt fails.

The parameter _COLLECT to store the lock request in a local lock container.

To send the content of the lock container with the  FM: FLUSH_ENQUEUE

Lock Mode:
E-Write Lock-(allow accumulation of locks)
S-Read Lock
X-Exclusive, (not allow  accumulation of locks)

 

BASIC ABAP PROGRAMS & INTERFACE CREATION

Type group also known as type pool are standalone program they do not contain any executable code but only contain TYPE definition & CONSTANT definition.

Function modules are always defined globally, whereas method is defined either globally or locally.
Function modules do not provide returning values.

Subroutines do not provide input or output parameters directly because both USING & CHANGING are treated as type of changing parameter; they do not provide for returning values.

Pass by reference is always preferable when performance is an issue, whereas pass by value is more suitable for situation where robustness and data consistency are important.

ABAP EVENT BLOCKS

Within event blocks you cannot declare local data type or data objects.
The event AT SELECTION-SCREEN & GET can contain local data type or data objects

1 .LOAD-OF-PROGRAM - This event is only triggered once
2 .INITIALIZATION -
3 .AT-SELECTION-SCREEN-OUTPUT     
4. AT SELECTION-SCREEN
5. START-OF-SELECTION
6.GET node
7.END-OF-SELECTION

The Events in ABAP are,
Classical Events.
1) Initialization
2) Load of Program
3) At selection-screen output
4) At Selection-Screen of Field
5) At Selection-Screen on Value-Request
6) At Selection-Screen on Help-Request
7) At Selection-Screen
8) Start of Selection
9) End of Selection
10) Top of Page
11) End of Page

Interactive Events
12) At Line-Selection.
13) At PF key
14) At User-Command
15) Top-of-page During Line-Selection.

Module pool Programming events are
1) PAI - Process After Input
2) PBO - Process Before Output
3) POV - Process On Value Request (F1 HELP)

IS REQUESTED and IS SUPPLIED are the two special keywords supplied by SAP for use in function modules. 
IS REQUESTED: 
Consider the following code in a function module:
  If CARRNAME is requested.
    Select single CARRNAME from SCARR
        Where carrid eq I_carrid.
  Endif.

The statement “If CARRNAME is requested” is true if the actual parameter was specified for the formal parameter CARRID, when the function module call was made. IS REQUESTED is allowed only in a function module and not even in a subroutine called by the function module. Suppose the call to the above function module in the program is as follows:
CALL FUNCTION 'ZSURESH_TEST1'
EXPORTING
     CARRID = 'AA'
IMPORTING
   CONNID = connid
*  FLDATE =
*  CARRNAME = carrname .
Since CARRNAME value is not requested in the program, the statement “If CARRNAME is requested” fails, thus avoiding unnecessary expensive database operation.
IS SUPPLIED:
This checks whether the parameter was passed during runtime (IMPORTING). For this the parameter should be optional, else the system raises an error. This statement can be used in function modules and methods.
AUTHORIZATION CHECKS

AUTHORITY-CHECK OBJECT 'M_EINF_WRK'
    ID 'WERKS' FIELD '0002'
    ID 'ACTVT' FIELD '02'.
 AUTHORITY-CHECK OBJECT 'M_EINF_WRK'
    ID 'WERKS' DUMMY
    ID 'ACTVT' FIELD '01':

authority-check object 'Z_TCODE'
id 'ACTVT' field '03' " read access
id 'ZTCODE' field p_tcode. " actual value

ABAP DICTIONARY

In ABAP dictionary we create data types such as
1: data element
2.structures
3.table type

The ABAP Dictionary has 24 predefined data types.

The conversion routine for the domain is identified as a five-character name, and it generate two-function module for the conversion routine.

1. The CONVERSION_EXIT_XXXXX_INPUT
2. The CONVERSION_EXIT_XXXXX_OUTPUT

To create data elements in the ABAP dictionary you have to define data type.
The data type for the data element could be Elementary Type or Reference Type.
For Elementary data type you have to option to assign domain or predefined.

Structures.
In ABAP dictionary we can define flat, nested or deep structure.

Table Types
1. Line type
2.Access Mode
3.Key

Attaching search help to the table field is only possible if the table field is assigned to data elements. Otherwise, if you are using predefined ABAP dictionary search help for the table field is not possible

UNICODE

From Release 6.10 onward, the SAP NetWeaver Application Server supports both Unicode & non-Unicode systems.

Non-Unicode systems are conventional ABAP system, in which one character is usually represented by one byte.
Unicode systems are ABAP system that are based on Unicode character set and that have corresponding underlying operating system & database.

In Unicode programs, only the following elementary data objects are now character-type:

Data type	Meaning
C	Text field
D	Date field
N	Numerical text
T	Time field
String	Text string

In Unicode programs, elementary data objects of types X and XSTRING are byte-type.

In Unicode, an offset and/or length specification for a structure is only permitted if the structure is
a) Character Type
b) Flat

In addition, structures are character-type if they contain only flat character-type components (only components from the above table with the exception of text strings).

Two structures in Unicode programs are only compatible when all alignment gaps are identical on all platforms.

SAP supports the representations UTF-8, UTF-16, and UTF-32, and the byte order can be platform-dependent.

When opening a file in TEXT MODE, the ENCODING addition must be used to specify the character representation.
When opening a file in LEGACY MODE, the byte order (endian) and a non-Unicode code page must be specified.

CLASSICAL SCREENS

Selection screen are created for an executable program and screen flow logic is required for dialog screens.
For screen in a module pool program type M, the start screen is specified in the transaction code you assign to the module pool.

CLEAR :  It will clear only Header of the internal Table.

Clear[]: it will clear the content of the internal table

Refresh  : It will clear the Data in that internal table,but allocated memory will

               remain.

Free  :  It will clear the data as well as allocated memory for that internal table.

The default next screen is defined in the Screen Painter

The next screen number can be changed dynamically in the PAI flow logic by the ABAP statement SET SCREEN

The screen flow logic consists of
1. Process Before Output (PBO)
2.Process After Input(PAI)
3.Process On Help-Request(POH)
4.Process On Value-Request(POV)

The screen flow logic must contain at least PBO and PAI events.

The screen type can be normal screen, sub screen, or dialog box.

The graphical layout editor has three buttons
1.Maintain Element Attributes
2.Get Dictionary/Program Fields
3.Show element List

Each screen has a 20-charcter OK field which is not displayed in the screen and which you must name. The OK field is also referred to as the function code.
You also need to declare a data variable with exactly the same name of type SY-UCOMM.

The field SY-DYNNR refer to current screen number.

Screen Numbers:

         1000 – Selection Screen

   >= 9000 – Custom Screen

9000-9500 – SAP Partners

      >9500 – Customer Screen

The FIELD statement is used in PAI, POH & POV.

The GUI status & GUI title together make up the user interface for the screen.

The GUI status consists of menu bar, standard tool bar, application toolbar &function key & GUI TITLE

A menu bar is made up of individual menus and can have up to EIGHT menus including the SYSTEM & HELP menu.

Each menu can have up 15 entries or function

Functions within the menu or toolbars are identified by function codes
The attributes FUNCTION TYPE  is also sometimes referred to as functional type.

The Function Text is displayed as quick info for the icon or button.

The function key assignment consist of reserved function key, recommended function key & freely assigned function key.