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like Vs type; data object vs data element.

hi,

kindly tell me the difference between like and type and how does it differ when writing a code or what will be the differernce in the output and what is the difference between data object and data type.thanks in advance.

regards

rittik

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  • author's profile photo Former Member
    Former Member
    Posted on Dec 27, 2007 at 06:40 AM

    hi Rittik,

    The following could provide u the brief idea...

    Like v/s Type

    Using the additions TYPE or LIKE in the TYPESstatement, local data types in a program can be referred to known data types or data objects. This is mainly the case with user-defined elementary data types. If you declare variables using the additions TYPE type or LIKE dobj with statement DATA, the data type of var is already fully defined before the declaration is made.

    The known types or data that are referred to must be visible at the point where the data type or variable is declared.

    A known data type can be any of the following:

    · A predefined ABAP type to which you refer using the TYPE addition

    · An existing local data type in the program to which you refer using the TYPE addition

    · The data type of a local data object in the program to which you refer using the LIKE addition

    · A data type in the ABAP Dictionary to which you refer using the TYPE addition. To ensure compatibility with earlier releases, it is still possible to use the LIKE addition to refer to database tables and flat structures in the ABAP Dictionary. However, you should use the TYPE addition in new programs.

    Data Object

    Data Objects

    Data objects are the physical units with which ABAP statements work at runtime. The contents of a data object occupy memory space in the program. ABAP statements access these contents by addressing the name of the data object and interpret them according to the data type.. For example, statements can write the contents of data objects in lists or in the database, they can pass them to and receive them from routines, they can change them by assigning new values, and they can compare them in logical expressions.

    Each ABAP data object has a set of technical attributes, which are fully defined at all times when an ABAP program is running (field length, number of decimal places, and data type). You declare data objects either statically in the declaration part of an ABAP program (the most important statement for this is DATA), or dynamically at runtime (for example, when you call procedures). As well as fields in the memory area of the program, the program also treats literals like data objects.

    Data Element

    data element describes either an elementary type or a reference type.

    An elementary type is defined by the built-in data type, length and possibly the number of decimal places. These type attributes can either be defined directly in the data element or copied from a domain.

    A reference type defines the types of reference variables in ABAP programs.

    You can use a data element to define the type of a table field, structure component or the row type of a table type. A data element can also be referenced in ABAP programs with TYPE. As a result, variables that take on the attributes of a data element can be defined in an ABAP program.

    Reward if helpful.

    Thank you,

    Regards.

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  • author's profile photo Former Member
    Former Member
    Posted on Dec 27, 2007 at 06:42 AM

    The main difference between TYPE and LIKE parameter when defining or declaring the object is that TYPE is used to refer existing DATA TYPE (elementary or structured or user defined) while LIKE is used to declare data objects with reference to existing DATA OBJECTS.

    For all practical purposes there are the same. The only additional advantage with types is that you can define your own types(including complex ones) in the data dictionary and reuse them accross various programs.

    But within a program if two variables are defined one using LIKE and another using TYPE, both referring to the same field, then there is no difference.

    If I include a type pool within a program, then I can define my variables only using TYPE to refer to any type defined in that pool. I cannot use LIKE in this scenario. Also, if I want to use native types like C, N, etc, I cannot use LIKE there either. I can use LIKE ABC only if ABC is in the database or if ABC is defined previously in the same program.

    I can use TYPE ABC, if ABC is defined in database as a TYPE and included in the program with the statement TYPE-POOLS. I can use it, if it is the native types. I can use it, if it is already defined in the dictionary as a structure/table or structure/table field, or even if it is defined as a data element or a domain. So I can declare a variable V_BUKRS TYPE BUKRS, but I cannot define a variable V_BUKRS LIKE BUKRS.

    But if I intend to use V_BUKRS to store company code, I will prefer to declare it as V_BUKRS LIKE T001-BUKRS, only because if tomorrow for some reason, the definition of T001-BUKRS changes to a data element for example, BUKRS_N(say DEC 4) instead of the data element BUKRS(CHAR 4) that it refers to now, I don't have to change my programs because I am referring to the table field and inhereting its properties. Whereas, had I declared my V_BUKRS TYPE BUKRS and the table now changed to BUKRS_N, I will be forced to change my program as there will be a type incompatability.

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  • author's profile photo Former Member
    Former Member
    Posted on Dec 27, 2007 at 06:39 AM

    Data is used to create data object ( means memory will be allocated)

    Types is used to create structures

    Type is used to refer to Predefined data types ( like n,i,f,d,t,p,x....)

    Like is used to refer the local variables.

    All ABAP programs can define their own data types. Within a program, procedures can also define local types.

    You define local data types in a program using the

    TYPES attr.

    You can access the technical properties of an instance attribute using the class name and a reference variable without first having to create an object. The properties of the attributes of a class are not instance-specific and belong to the static properties of the class.

    TYPES: BEGIN OF struct,

    number_1 TYPE i,

    number_2 TYPE p DECIMALS 2,

    END OF struct.

    DATA: wa_struct TYPE struct,

    number LIKE wa_struct-number_2,

    date LIKE sy-datum,

    time TYPE t,

    text TYPE string,

    company TYPE s_carr_id.

    This example declares variables with reference to the internal type STRUCT in the program, a component of an existing data object wa_struct, the predefined data object SY-DATUM, the predefined ABAP type t and STRING, and the data element S_CARR_ID from the ABAP Dictionary.

    Referring to Generic Data Types

    If you refer to one of the generic predefined ABAP types of fixed length (c, n, p, x) in the TYPES or DATA statement, you must specify the undefined technical attributes.

    TYPES|DATA var(length) TYPE type DECIMALS dec...

    TYPES|DATA var TYPE type LENGTH len DECIMALS dec...

    DATA: text1,

    text2 LENGTH 2,

    text3 TYPE c LENGTH 3,

    pack TYPE p DECIMALS 2 VALUE '1.225'.

    This example creates three character variables with field lengths of one, two, and three bytes respectively, and a packed number variable with field length 8 bytes and two decimal places. If the attribute Fixed point arithmetic is set, the value of pack is 1.23.

    This example shows how to declare elementary data objects with reference to predefined ABAP types.

    PROGRAM demo_elementary_data_objects.

    DATA text1 TYPE c LENGTH 20.

    DATA text2 TYPE string.

    DATA number TYPE i.

    text1 = 'The number'.

    number = 100.

    text2 = 'is an integer.'.

    WRITE: text1, number, text2.

    This program produces the following output on the screen:

    The number 100 is an integer.

    In this example, the data objects text1, text2 and number are declared with the DATA statement. The technical attributes are determined by referring to the predefined ABAP types c, string, and I. Values from unnamed literals are assigned to the data objects. The contents of the named data objects are displayed on the list.

    Specifying a Start Value

    When you declare an elementary fixed-length variable, the DATAstatement automatically fills it with the type-specific initial value as listed in the table in the Predefined ABAP Types section.

    However, you can also specify a starting value of a fixed-length elementary variable (also within a structure declaration) using the VALUE addition in the DATAstatement:

    DATA var ... VALUE val|{IS INITIAL}.

    Specifying start values:

    DATA: counter TYPE p VALUE 1,

    date TYPE d VALUE '19980601',

    flag TYPE n VALUE IS INITIAL.

    After this data declaration, the character string flag contains its type specific

    Initial value ‘0’.

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  • author's profile photo Former Member
    Former Member
    Posted on Dec 27, 2007 at 06:43 AM

    Hi Sir ,

    Please have a look below .Hope it is suitable and simpler solution for your question.

    Please do reward if useful.

    Thankx.

    Each ABAP program define its own data types using the statement.

    TYPES dtype [TYPE type|LIKE dobj] ...

    and declare its own variables or instance attributes of classes using the statement

    DATA var [{TYPE type}|{LIKE dobj}] ...

    Within the program or a class, you can also define local data types and variables within procedures. Local variables in procedures obscure identically-named variables in the main program or class.

    When creating data types and data objects, there are a number of naming convention that also apply for other local program definitions, such as procedures. These are described in detail in the keyword documentation.

    The TYPE addition allows you to construct new data types in the TYPES, DATA; CONSTANTS; and STATICSstatements. In the TYPES statement, these are local data types in the program. In the other statements, they are attributes of new data objects, meaning that the newly defined data types are not free-standing. Rather, they are linked to database objects.This means that you can refer to them using the LIKEaddition, but not using TYPE.

    To construct new data types, the addition TYPE can be used with the following type constructors:

    � Construction of reference types

    REF TO type|dobj

    � Construction of structured data types

    BEGIN OF struc_type.

    ...

    END OF struc_type.

    � Construction of table types

    tabkind OF linetype [WITH key]

    These data types only exist during the runtime of the ABAP program.

    Referring to Known Data Types or Data Objects

    Using the additions TYPE or LIKE in the TYPESstatement, local data types in a program can be referred to known data types or data objects. This is mainly the case with user-defined elementary data types. If you declare variables using the additions TYPE type or LIKE dobj with statement DATA, the data type of var is already fully defined before the declaration is made.

    The known types or data that are referred to must be visible at the point where the data type or variable is declared.

    A known data type can be any of the following:

    � A predefined ABAP type to which you refer using the TYPE addition

    � An existing local data type in the program to which you refer using the TYPE addition

    � The data type of a local data object in the program to which you refer using the LIKE addition

    � A data type in the ABAP Dictionary to which you refer using the TYPE addition. To ensure compatibility with earlier releases, it is still possible to use the LIKE addition to refer to database tables and flat structures in the ABAP Dictionary. However, you should use the TYPE addition in new programs.

    The LIKE addition takes its technical attributes from a visible data object. As a rule, you can use LIKE to refer to any object that has been declared using DATA or a similar statement, and is visible in the current context. The data object only has to have been declared. It is irrelevant whether the data object already exists in memory when you make the LIKE reference.

    � In principle, the local data objects in the same program are visible. As with local data types, there is a difference between local data objects in procedures and global data objects. Data objects defined in a procedure obscure other objects with the same name that are declared in the global declarations of the program.

    � You can also refer to the data objects of other visible ABAP programs. These might be, for example, the visible attributes of global classes in class pools. If a global class cl_lobal has a public instance attribute or static attribute attr, you can refer to it as follows in any ABAP program:

    DATA dref TYPE REF TO cl_global.

    DATA: f1 LIKE cl_global=>attr,

    f2 LIKE dref->attr.

    You can access the technical properties of an instance attribute using the class name and a reference variable without first having to create an object. The properties of the attributes of a class are not instance-specific and belong to the static properties of the class.

    TYPES: BEGIN OF struct,

    number_1 TYPE i,

    number_2 TYPE p DECIMALS 2,

    END OF struct.

    DATA: wa_struct TYPE struct,

    number LIKE wa_struct-number_2,

    date LIKE sy-datum,

    time TYPE t,

    text TYPE string,

    company TYPE s_carr_id.

    This example declares variables with reference to the internal type STRUCT in the program, a component of an existing data object wa_struct, the predefined data object SY-DATUM, the predefined ABAP type t and STRING, and the data element S_CARR_ID from the ABAP Dictionary.

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  • author's profile photo Former Member
    Former Member
    Posted on Dec 27, 2007 at 06:43 AM

    Data types

    Data types are the actual type definitions in the ABAP Dictionary. They allow you to define elementary types, reference types, and complex types that are visible globally in the system. The data types of database tables are a subset of all possible types, namely flat structures.

    Data Elements

    Data elements in the ABAP Dictionary describe individual fields. They are the smallest indivisible units of the complex types described below, and are used to specify the types of columns in the database. Data elements can be elementary types or reference types.

    Structures

    A structure is a sequence of any other data types from the ABAP Dictionary, that is, data elements, structures, table types, or database tables. When you create a structure in the ABAP Dictionary, each component must have a name and a data type. In an ABAP program, you can use the TYPE addition to refer directly to a structure.

    If you define a local data type in a program by referring to a structure as follows:

    TYPES <t> TYPE <structure>.

    Table Types

    Table types are construction blueprints for internal tables that are stored in the ABAP Dictionary.

    When you create a table type in the ABAP Dictionary, you specify the line type, access type, and key. The line type can be any data type from the ABAP Dictionary, that is, a data element, a structure, a table type, or the type of a database table. You can also enter a predefined Dictionary type directly as the line type, in the same way that you can with a domain.

    Type Groups

    Before Release 4.5A, it was not possible to define standalone types in the ABAP Dictionary to which you could refer using a TYPE addition in an ABAP program. It was only possible to refer SAP AG BC - ABAP Programming

    Data Types in the ABAP Dictionary to flat structures. Structures in programs corresponded to the structures of database tables or structures in the ABAP Dictionary. In ABAP programs, you could only refer to database tables and structures in the ABAP Dictionary using LIKE. It was, however, possible to refer to individual components of the Dictionary type. Complex local data types such as internal tables or deep structures had no equivalent in the ABAP Dictionary. The solution to this from Release 3.0 onwards was to use type groups. Type groups were based on the include technique, and allowed you to store any type definitions globally in the Dictionary by defining them using TYPES statements.

    Views:

    There are 4 types views are avilable in SAP.

    Database View - To club more than one table

    Projection View - To hide fields in one table

    Maintanance View - To maintain database records in table

    Help View - To provide help for a fields (Same functionality as Search help. This is outdated)

    View are improves perfromance in the following aspects

    1. If you want to use more than two table in 'JOIN' condition better to use Views . It will improves performance of a program

    2. If you want to use mutiple FOR ALL ENTRIES clause, better to club all SELECT statement in a view.

    Lock Objects:

    Lock objects are use in SAP to avoid the inconsistancy at the time of data is being insert/change into database.

    SAP Provide three type of Lock objects.

    Read Lock(Shared Locked)

    protects read access to an object. The read lock allows other transactions read access but not write access to

    the locked area of the table

    Write Lock(exclusive lock)

    protects write access to an object. The write lock allows other transactions neither read nor write access to

    the locked area of the table.

    Enhanced write lock (exclusive lock without cumulating)

    works like a write lock except that the enhanced write lock also protects from further accesses from the

    same transaction.

    You can create a lock on a object of SAP thorugh transaction SE11 and enter any meaningful name start with EZ Example EZTEST_LOCK.

    Use: you can see in almost all transaction when you are open an object in Change mode SAP could not allow to any other user to open the same object in change mode.

    Example: in HR when we are enter a personal number in master data maintainance screen SAP can't allow to any other user to use same personal number for changes.

    Technicaly:

    When you create a lock object System automatically creat two function module.

    1. ENQUEUE_<Lockobject name>. to insert the object in a queue.

    2. DEQUEUE_<Lockobject name>. To remove the object is being queued through above FM.

    You have to use these function module in your program.

    Search Helps:

    These are two types.

    Elementary n Collective.

    1) Elementary search helps describe a search path. The elementary search help must define where the data of the hit list should be read from (selection method), how the exchange of values between the screen template and selection method is implemented (interface of the search help) and how the online input help should be defined (online behavior of the search help).

    2) Collective search helps combine several elementary search helps. A collective search help thus can offer several alternative search paths.

    3)An elementary search help defines the standard flow of an input help.

    4) A collective search help combines several elementary search helps. The user can thus choose one of several alternative search paths with a collective search help.

    5)A collective search help comprises several elementary search helps. It combines all the search paths that are meaningful for a field.

    6)Both elementary search helps and other search helps can be included in a collective search help. If other collective search helps are contained in a collective search help, they are expanded to the level of the elementary search helps when the input help is called.

    See the below link to understand this completely:

    http://help.sap.com/saphelp_nw2004s/helpdata/en/cf/21ee93446011d189700000e8322d00/frameset.htm

    Rewards if useful.

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