regarding internal tables

Former Member · ‎04-02-2008

Hi

can you send syntaxes for declaring different types of internal tables(standard,sorted,hash)

Former Member · ‎04-02-2008

Hi,

Check this link

http://www.sap-img.com/abap/what-are-different-types-of-internal-tables-and-their-usage.htm

http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb35de358411d1829f0000e829fbfe/content.htm

Thanks

Reward if helpful.

Former Member · ‎04-02-2008

Standard tables

This is the most appropriate type if you are going to address the individual table entries using the index. Index access is the quickest possible access. You should fill a standard table by appending lines (ABAP APPEND statement), and read, modify and delete entries by specifying the index (INDEX option with the relevant ABAP command). The access time for a standard table increases in a linear relationship with the number of table entries. If you need key access, standard tables are particularly useful if you can fill and process the table in separate steps. For example, you could fill the table by appending entries, and then sort it. If you use the binary search option with key access, the response time is logarithmically proportional to the number of table entries.

Sorted tables

This is the most appropriate type if you need a table which is sorted as you fill it. You fill sorted tables using the INSERT statement. Entries are inserted according to the sort sequence defined through the table key. Any illegal entries are recognized as soon as you try to add them to the table. The response time for key access is logarithmically proportional to the number of table entries, since the system always uses a binary search. Sorted tables are particularly useful for partially sequential processing in a LOOP if you specify the beginning of the table key in the WHERE condition.

Hashed tables

This is the most appropriate type for any table where the main operation is key access. You cannot access a hashed table using its index. The response time for key access remains constant, regardless of the number of table entries. Like database tables, hashed tables always have a unique key. Hashed tables are useful if you want to construct and use an internal table which resembles a database table or for processing large amounts of data.

DATA ITAB TYPE HASHED TABLE OF SPFLI

WITH UNIQUE KEY CARRID CONNID.

The table object ITAB has the type hashed table, a line type corresponding to the flat structure SPFLI from the ABAP Dictionary, and a unique key with the key fields CARRID and CONNID. The internal table ITAB can be regarded as an internal template for the database table SPFLI. It is therefore particularly suitable for working with data from this database table as long as you only access it using the key.

Like all local data types in programs , you define internal tables using the TYPES statement. If you do not refer to an existing table type using the TYPE or LIKE addition, you can use the TYPES statement to construct a new local internal table in your program.

TYPES <t> TYPE|LIKE <tabkind> OF <linetype> [WITH <key>]

[INITIAL SIZE <n>].

After TYPE or LIKE, there is no reference to an existing data type. Instead, the type constructor occurs:

<tabkind> OF <linetype> [WITH <key>]

The type constructor defines the table type <tabkind>, the line type <linetype>, and the key <key> of the internal table <t>.

You can, if you wish, allocate an initial amount of memory to the internal table using the INITIAL SIZE addition.

Table type

You can specify the table type <tabkind> as follows:

Generic table types

INDEX TABLE

For creating a generic table type with index access.

ANY TABLE

For creating a fully-generic table type.

Data types defined using generic types can currently only be used for field symbols and for interface parameters in procedures . The generic type INDEX TABLE includes standard tables and sorted tables. These are the two table types for which index access is allowed. You cannot pass hashed tables to field symbols or interface parameters defined in this way. The generic type ANY TABLE can represent any table. You can pass tables of all three types to field symbols and interface parameters defined in this way. However, these field symbols and parameters will then only allow operations that are possible for all tables, that is, index operations are not allowed.

Fully-Specified Table Types

STANDARD TABLE or TABLE

For creating standard tables.

SORTED TABLE

For creating sorted tables.

HASHED TABLE

For creating hashed tables.

Fully-specified table types determine how the system will access the entries in the table in key operations. It uses a linear search for standard tables, a binary search for sorted tables, and a search using a hash algorithm for hashed tables.

Line type

For the line type <linetype>, you can specify:

Any data type if you are using the TYPE addition. This can be a predefined ABAP type, a local type in the program, or a data type from the ABAP Dictionary. If you specify any of the generic elementary types C, N, P, or X, any attributes that you fail to specify (field length, number of decimal places) are automatically filled with the default values. You cannot specify any other generic types.

Any data object recognized within the program at that point if you are using the LIKE addition. The line type adopts the fully-specified data type of the data object to which you refer. Except for within classes, you can still use the LIKE addition to refer to database tables and structures in the ABAP Dictionary (for compatibility reasons).

All of the lines in the internal table have the fully-specified technical attributes of the specified data type.

Key

You can specify the key <key> of an internal table as follows:

[UNIQUE|NON-UNIQUE] KEY <col1> ... <col n>

In tables with a structured line type, all of the components <coli> belong to the key as long as they are not internal tables or references, and do not contain internal tables or references. Key fields can be nested structures. The substructures are expanded component by component when you access the table using the key. The system follows the sequence of the key fields.

[UNIQUE|NON-UNIQUE] KEY TABLE LINE

If a table has an elementary line type (C, D, F, I, N, P, T, X), you can define the entire line as the key. If you try this for a table whose line type is itself a table, a syntax error occurs. If a table has a structured line type, it is possible to specify the entire line as the key. However, you should remember that this is often not suitable.

[UNIQUE|NON-UNIQUE] DEFAULT KEY

This declares the fields of the default key as the key fields. If the table has a structured line type, the default key contains all non-numeric columns of the internal table that are not and do not contain references or internal tables. If the table has an elementary line type, the default key is the entire line. The default key of an internal table whose line type is an internal table, the default key is empty.

Specifying a key is optional. If you do not specify a key, the system defines a table type with an arbitrary key. You can only use this to define the types of field symbols and the interface parameters of procedures . For exceptions, refer to Special Features of Standard Tables.

The optional additions UNIQUE or NON-UNIQUE determine whether the key is to be unique or non-unique, that is, whether the table can accept duplicate entries. If you do not specify UNIQUE or NON-UNIQUE for the key, the table type is generic in this respect. As such, it can only be used for specifying types. When you specify the table type simultaneously, you must note the following restrictions:

You cannot use the UNIQUE addition for standard tables. The system always generates the NON-UNIQUE addition automatically.

You must always specify the UNIQUE option when you create a hashed table.

Initial Memory Requirement

You can specify the initial amount of main memory assigned to an internal table object when you define the data type using the following addition:

INITIAL SIZE <n>

This size does not belong to the data type of the internal table, and does not affect the type check. You can use the above addition to reserve memory space for <n> table lines when you declare the table object.

When this initial area is full, the system makes twice as much extra space available up to a limit of 8KB. Further memory areas of 12KB each are then allocated.

You can usually leave it to the system to work out the initial memory requirement. The first time you fill the table, little memory is used. The space occupied, depending on the line width, is 16 <= <n> <= 100.

It only makes sense to specify a concrete value of <n> if you can specify a precise number of table entries when you create the table and need to allocate exactly that amount of memory (exception: Appending table lines to ranked lists). This can be particularly important for deep-structured internal tables where the inner table only has a few entries (less than 5, for example).

To avoid excessive requests for memory, large values of <n> are treated as follows: The largest possible value of <n> is 8KB divided by the length of the line. If you specify a larger value of <n>, the system calculates a new value so that n times the line width is around 12KB.

Examples


TYPES: BEGIN OF LINE,
COLUMN1 TYPE I,
COLUMN2 TYPE I,
COLUMN3 TYPE I,
END OF LINE.

TYPES ITAB TYPE SORTED TABLE OF LINE WITH UNIQUE KEY COLUMN1.

The program defines a table type ITAB. It is a sorted table, with line type of the structure LINE and a unique key of the component COLUMN1.



TYPES VECTOR TYPE HASHED TABLE OF I WITH UNIQUE KEY TABLE LINE.

TYPES: BEGIN OF LINE,
COLUMN1 TYPE I,
COLUMN2 TYPE I,
COLUMN3 TYPE I,
END OF LINE.

TYPES ITAB TYPE SORTED TABLE OF LINE WITH UNIQUE KEY COLUMN1.

TYPES: BEGIN OF DEEPLINE,
FIELD TYPE C,
TABLE1 TYPE VECTOR,
TABLE2 TYPE ITAB,
END OF DEEPLINE.

TYPES DEEPTABLE TYPE STANDARD TABLE OF DEEPLINE 
WITH DEFAULT KEY.

The program defines a table type VECTOR with type hashed table, the elementary line type I and a unique key of the entire table line. The second table type is the same as in the previous example. The structure DEEPLINE contains the internal table as a component. The table type DEEPTABLE has the line type DEEPLINE. Therefore, the elements of this internal table are themselves internal tables. The key is the default key - in this case the column FIELD. The key is non-unique, since the table is a standard table.

Former Member · ‎04-02-2008

Hi Venkatesh,

Table type: The table type determines how ABAP accesses individual table rows. Based on the table type, internal tables can be subdivided into the following three categories:

In Standard tables, a logical index is set up internally. The data can be accessed using the table index or the key. If the data is accessed using the key, the response time depends linearly on the number of table entries. The key of a standard table is always non-unique. When you define the table, you must not specify uniqueness for the key.

Sorted tables are always stored sorted by the key. Also for sorted tables, a logical index is set up internally. The data can be accessed using the table index or the key. If the data is accessed using the key, the response time depends logarithmically on the number of table entries since the data is accessed through a binary search. The key of sorted tables can be unique or non-unique. When you define the table, you must specify whether the key is UNIQUE or NON-UNIQUE.

Standard tables and sorted tables are also commonly referred to as index tables.

In hash tables, no logical index is set up internally. Hash tables can only be accessed by specifying the key. The response time in this case is constant irrespective of the number of table entries since the data is accessed through a hash algorithm. The key of hash tables must be unique. When you define the table, you must specify the key as UNIQUE.

DECLARATION SYNTAX:

DATA itab { {TYPE <tabkind> OF {REF TO} type}

| {LIKE <tabkind> OF <dobj>} }

{WITH key} {INITIAL SIZE n}

{WITH HEADER LINE}

{VALUE IS INITIAL}

{READ-ONLY}.

where <tabkind> may be any of the following values.

STANDARD TABLE, SORTED TABLE, HASHED TABLE, ANY TABLE or INDEX TABLE.

n = any number

Hope this clear to you now. Reward if useful.

Thanks and Regards,

Maddineni Bharath.

Former Member · ‎04-02-2008

hi venkatesh,

i am providing the complete info on internal tables.pls chk it out.

Internal tables

Internal tables provide a means of taking data from a fixed structure and storing it in working memory in ABAP. The data is stored line by line in memory, and each line has the same structure. In ABAP, internal tables fulfill the function of arrays. Since they are dynamic data objects, they save the programmer the task of dynamic memory management in his or her programs. You should use internal tables whenever you want to process a dataset with a fixed structure within a program. A particularly important use for internal tables is for storing and formatting data from a database table within a program. They are also a good way of including very complicated data structures in an ABAP program.

Like all elements in the ABAP type concept, internal tables can exist both as data types and as data objects A data type is the abstract description of an internal table, either in a program or centrally in the ABAP Dictionary, that you use to create a concrete data object. The data type is also an attribute of an existing data object.

Internal Tables as Data Types

Internal tables and structures are the two structured data types in ABAP. The data type of an internal table is fully specified by its line type, key, and table type.

Line type

The line type of an internal table can be any data type. The data type of an internal table is normally a structure. Each component of the structure is a column in the internal table. However, the line type may also be elementary or another internal table.

Key

The key identifies table rows. There are two kinds of key for internal tables - the standard key and a user-defined key. You can specify whether the key should be UNIQUE or NON-UNIQUE. Internal tables with a unique key cannot contain duplicate entries. The uniqueness depends on the table access method.

If a table has a structured line type, its default key consists of all of its non-numerical columns that are not references or themselves internal tables. If a table has an elementary line type, the default key is the entire line. The default key of an internal table whose line type is an internal table, the default key is empty.

The user-defined key can contain any columns of the internal table that are not references or themselves internal tables. Internal tables with a user-defined key are called key tables. When you define the key, the sequence of the key fields is significant. You should remember this, for example, if you intend to sort the table according to the key.

Table type

The table type determines how ABAP will access individual table entries. Internal tables can be divided into three types:

Standard tables have an internal linear index. From a particular size upwards, the indexes of internal tables are administered as trees. In this case, the index administration overhead increases in logarithmic and not linear relation to the number of lines. The system can access records either by using the table index or the key. The response time for key access is proportional to the number of entries in the table. The key of a standard table is always non-unique. You cannot specify a unique key. This means that standard tables can always be filled very quickly, since the system does not have to check whether there are already existing entries.

Sorted tables are always saved sorted by the key. They also have an internal index. The system can access records either by using the table index or the key. The response time for key access is logarithmically proportional to the number of table entries, since the system uses a binary search. The key of a sorted table can be either unique or non-unique. When you define the table, you must specify whether the key is to be unique or not. Standard tables and sorted tables are known generically as index tables.

Hashed tables have no linear index. You can only access a hashed table using its key. The response time is independent of the number of table entries, and is constant, since the system access the table entries using a hash algorithm. The key of a hashed table must be unique. When you define the table, you must specify the key as UNIQUE.

Generic Internal Tables

Unlike other local data types in programs, you do not have to specify the data type of an internal table fully. Instead, you can specify a generic construction, that is, the key or key and line type of an internal table data type may remain unspecified. You can use generic internal tables to specify the types of field symbols and the interface parameters of procedures . You cannot use them to declare data objects.

Internal Tables as Dynamic Data Objects

Data objects that are defined either with the data type of an internal table, or directly as an internal table, are always fully defined in respect of their line type, key and access method. However, the number of lines is not fixed. Thus internal tables are dynamic data objects, since they can contain any number of lines of a particular type. The only restriction on the number of lines an internal table may contain are the limits of your system installation. The maximum memory that can be occupied by an internal table (including its internal administration) is 2 gigabytes. A more realistic figure is up to 500 megabytes. An additional restriction for hashed tables is that they may not contain more than 2 million entries. The line types of internal tables can be any ABAP data types - elementary, structured, or internal tables. The individual lines of an internal table are called table lines or table entries. Each component of a structured line is called a column in the internal table.

Choosing a Table Type

The table type (and particularly the access method) that you will use depends on how the typical internal table operations will be most frequently executed.

Standard tables

This is the most appropriate type if you are going to address the individual table entries using the index. Index access is the quickest possible access. You should fill a standard table by appending lines (ABAP APPEND statement), and read, modify and delete entries by specifying the index (INDEX option with the relevant ABAP command). The access time for a standard table increases in a linear relationship with the number of table entries. If you need key access, standard tables are particularly useful if you can fill and process the table in separate steps. For example, you could fill the table by appending entries, and then sort it. If you use the binary search option with key access, the response time is logarithmically proportional to the number of table entries.

Sorted tables

This is the most appropriate type if you need a table which is sorted as you fill it. You fill sorted tables using the INSERT statement. Entries are inserted according to the sort sequence defined through the table key. Any illegal entries are recognized as soon as you try to add them to the table. The response time for key access is logarithmically proportional to the number of table entries, since the system always uses a binary search. Sorted tables are particularly useful for partially sequential processing in a LOOP if you specify the beginning of the table key in the WHERE condition.

Hashed tables

This is the most appropriate type for any table where the main operation is key access. You cannot access a hashed table using its index. The response time for key access remains constant, regardless of the number of table entries. Like database tables, hashed tables always have a unique key. Hashed tables are useful if you want to construct and use an internal table which resembles a database table or for processing large amounts of data.

Creating Internal Tables

Like other elements in the ABAP type concept, you can declare internal tables as abstract data types in programs or in the ABAP Dictionary, and then use them to define data objects. Alternatively, you can define them directly as data objects. When you create an internal table as a data object, you should ensure that only the administration entry which belongs to an internal table is declared statically. The minimum size of an internal table is 256 bytes. This is important if an internal table occurs as a component of an aggregated data object, since even empty internal tables within tables can lead to high memory usage. (In the next functional release, the size of the table header for an initial table will be reduced to 8 bytes). Unlike all other ABAP data objects, you do not have to specify the memory required for an internal table. Table rows are added to and deleted from the table dynamically at runtime by the various statements for adding and deleting records.

Internal table types

This section describes how to define internal tables locally in a program. You can also define internal tables globally as data types in the ABAP Dictionary.

Like all local data types in programs , you define internal tables using the TYPES statement. If you do not refer to an existing table type using the TYPE or LIKE addition, you can use the TYPES statement to construct a new local internal table in your program.

TYPES <t> TYPE|LIKE <tabkind> OF <linetype> [WITH <key>]

[INITIAL SIZE <n>].

After TYPE or LIKE, there is no reference to an existing data type. Instead, the type constructor occurs:

<tabkind> OF <linetype> [WITH <key>]

The type constructor defines the table type <tabkind>, the line type <linetype>, and the key <key> of the internal table <t>.

You can, if you wish, allocate an initial amount of memory to the internal table using the INITIAL SIZE addition.

Table type

You can specify the table type <tabkind> as follows:

Generic table types

INDEX TABLE

For creating a generic table type with index access.

ANY TABLE

For creating a fully-generic table type.

Data types defined using generic types can currently only be used for field symbols and for interface parameters in procedures . The generic type INDEX TABLE includes standard tables and sorted tables. These are the two table types for which index access is allowed. You cannot pass hashed tables to field symbols or interface parameters defined in this way. The generic type ANY TABLE can represent any table. You can pass tables of all three types to field symbols and interface parameters defined in this way. However, these field symbols and parameters will then only allow operations that are possible for all tables, that is, index operations are not allowed.

Fully-Specified Table Types

STANDARD TABLE or TABLE

For creating standard tables.

SORTED TABLE

For creating sorted tables.

HASHED TABLE

For creating hashed tables.

Fully-specified table types determine how the system will access the entries in the table in key operations. It uses a linear search for standard tables, a binary search for sorted tables, and a search using a hash algorithm for hashed tables.

Line type

For the line type <linetype>, you can specify:

Any data type if you are using the TYPE addition. This can be a predefined ABAP type, a local type in the program, or a data type from the ABAP Dictionary. If you specify any of the generic elementary types C, N, P, or X, any attributes that you fail to specify (field length, number of decimal places) are automatically filled with the default values. You cannot specify any other generic types.

Any data object recognized within the program at that point if you are using the LIKE addition. The line type adopts the fully-specified data type of the data object to which you refer. Except for within classes, you can still use the LIKE addition to refer to database tables and structures in the ABAP Dictionary (for compatibility reasons).

All of the lines in the internal table have the fully-specified technical attributes of the specified data type.

Key

You can specify the key <key> of an internal table as follows:

[UNIQUE|NON-UNIQUE] KEY <col1> ... <col n>

In tables with a structured line type, all of the components <coli> belong to the key as long as they are not internal tables or references, and do not contain internal tables or references. Key fields can be nested structures. The substructures are expanded component by component when you access the table using the key. The system follows the sequence of the key fields.

[UNIQUE|NON-UNIQUE] KEY TABLE LINE

If a table has an elementary line type (C, D, F, I, N, P, T, X), you can define the entire line as the key. If you try this for a table whose line type is itself a table, a syntax error occurs. If a table has a structured line type, it is possible to specify the entire line as the key. However, you should remember that this is often not suitable.

[UNIQUE|NON-UNIQUE] DEFAULT KEY

This declares the fields of the default key as the key fields. If the table has a structured line type, the default key contains all non-numeric columns of the internal table that are not and do not contain references or internal tables. If the table has an elementary line type, the default key is the entire line. The default key of an internal table whose line type is an internal table, the default key is empty.

Specifying a key is optional. If you do not specify a key, the system defines a table type with an arbitrary key. You can only use this to define the types of field symbols and the interface parameters of procedures . For exceptions, refer to Special Features of Standard Tables.

The optional additions UNIQUE or NON-UNIQUE determine whether the key is to be unique or non-unique, that is, whether the table can accept duplicate entries. If you do not specify UNIQUE or NON-UNIQUE for the key, the table type is generic in this respect. As such, it can only be used for specifying types. When you specify the table type simultaneously, you must note the following restrictions:

You cannot use the UNIQUE addition for standard tables. The system always generates the NON-UNIQUE addition automatically.

You must always specify the UNIQUE option when you create a hashed table.

Initial Memory Requirement

You can specify the initial amount of main memory assigned to an internal table object when you define the data type using the following addition:

INITIAL SIZE <n>

This size does not belong to the data type of the internal table, and does not affect the type check. You can use the above addition to reserve memory space for <n> table lines when you declare the table object.

When this initial area is full, the system makes twice as much extra space available up to a limit of 8KB. Further memory areas of 12KB each are then allocated.

You can usually leave it to the system to work out the initial memory requirement. The first time you fill the table, little memory is used. The space occupied, depending on the line width, is 16 <= <n> <= 100.

It only makes sense to specify a concrete value of <n> if you can specify a precise number of table entries when you create the table and need to allocate exactly that amount of memory (exception: Appending table lines to ranked lists). This can be particularly important for deep-structured internal tables where the inner table only has a few entries (less than 5, for example).

To avoid excessive requests for memory, large values of <n> are treated as follows: The largest possible value of <n> is 8KB divided by the length of the line. If you specify a larger value of <n>, the system calculates a new value so that n times the line width is around 12KB.

Examples

TYPES: BEGIN OF LINE,

COLUMN1 TYPE I,

COLUMN2 TYPE I,

COLUMN3 TYPE I,

END OF LINE.

TYPES ITAB TYPE SORTED TABLE OF LINE WITH UNIQUE KEY COLUMN1.

The program defines a table type ITAB. It is a sorted table, with line type of the structure LINE and a unique key of the component COLUMN1.

TYPES VECTOR TYPE HASHED TABLE OF I WITH UNIQUE KEY TABLE LINE.

TYPES: BEGIN OF LINE,

COLUMN1 TYPE I,

COLUMN2 TYPE I,

COLUMN3 TYPE I,

END OF LINE.

TYPES ITAB TYPE SORTED TABLE OF LINE WITH UNIQUE KEY COLUMN1.

TYPES: BEGIN OF DEEPLINE,

FIELD TYPE C,

TABLE1 TYPE VECTOR,

TABLE2 TYPE ITAB,

END OF DEEPLINE.

TYPES DEEPTABLE TYPE STANDARD TABLE OF DEEPLINE

WITH DEFAULT KEY.

The program defines a table type VECTOR with type hashed table, the elementary line type I and a unique key of the entire table line. The second table type is the same as in the previous example. The structure DEEPLINE contains the internal table as a component. The table type DEEPTABLE has the line type DEEPLINE. Therefore, the elements of this internal table are themselves internal tables. The key is the default key - in this case the column FIELD. The key is non-unique, since the table is a standard table.

Internal table objects

Internal tables are dynamic variable data objects. Like all variables, you declare them using the DATA statement. You can also declare static internal tables in procedures using the STATICS statement, and static internal tables in classes using the CLASS-DATA statement. This description is restricted to the DATA statement. However, it applies equally to the STATICS and CLASS-DATA statements.

Reference to Declared Internal Table Types

Like all other data objects, you can declare internal table objects using the LIKE or TYPE addition of the DATA statement.

DATA <itab> TYPE <type>|LIKE <obj> [WITH HEADER LINE].

Here, the LIKE addition refers to an existing table object in the same program. The TYPE addition can refer to an internal type in the program declared using the TYPES statement, or a table type in the ABAP Dictionary.

You must ensure that you only refer to tables that are fully typed. Referring to generic table types (ANY TABLE, INDEX TABLE) or not specifying the key fully is not allowed (for exceptions, refer to Special Features of Standard Tables).

The optional addition WITH HEADER line declares an extra data object with the same name and line type as the internal table. This data object is known as the header line of the internal table. You use it as a work area when working with the internal table (see Using the Header Line as a Work Area). When you use internal tables with header lines, you must remember that the header line and the body of the table have the same name. If you have an internal table with header line and you want to address the body of the table, you must indicate this by placing brackets after the table name (<itab>[]). Otherwise, ABAP interprets the name as the name of the header line and not of the body of the table. You can avoid this potential confusion by using internal tables without header lines. In particular, internal tables nested in structures or other internal tables must not have a header line, since this can lead to ambiguous expressions.

TYPES VECTOR TYPE SORTED TABLE OF I WITH UNIQUE KEY TABLE LINE.

DATA: ITAB TYPE VECTOR,

JTAB LIKE ITAB WITH HEADER LINE.

MOVE ITAB TO JTAB. <- Syntax error!

MOVE ITAB TO JTAB[].

The table object ITAB is created with reference to the table type VECTOR. The table object JTAB has the same data type as ITAB. JTAB also has a header line. In the first MOVE statement, JTAB addresses the header line. Since this has the data type I, and the table type of ITAB cannot be converted into an elementary type, the MOVE statement causes a syntax error. The second MOVE statement is correct, since both operands are table objects.

Declaring New Internal Tables

You can use the DATA statement to construct new internal tables as well as using the LIKE or TYPE addition to refer to existing types or objects. The table type that you construct does not exist in its own right; instead, it is only an attribute of the table object. You can refer to it using the LIKE addition, but not using TYPE. The syntax for constructing a table object in the DATA statement is similar to that for defining a table type in the TYPES statement.

DATA <itab> TYPE|LIKE <tabkind> OF <linetype> WITH <key>

[INITIAL SIZE <n>]

[WITH HEADER LINE].

As when you define a table type , the type constructor

defines the table type <tabkind>, the line type <linekind>, and the key <key> of the internal table <itab>. Since the technical attributes of data objects are always fully specified, the table must be fully specified in the DATA statement. You cannot create generic table types (ANY TABLE, INDEX TABLE), only fully-typed tables (STANDARD TABLE, SORTED TABLE, HASHED TABLE). You must also specify the key and whether it is to be unique (for exceptions, refer to Special Features of Standard Tables).

As in the TYPES statement, you can, if you wish, allocate an initial amount of memory to the internal table using the INITIAL SIZE addition. You can create an internal table with a header line using the WITH HEADER LINE addition. The header line is created under the same conditions as apply when you refer to an existing table type.

DATA ITAB TYPE HASHED TABLE OF SPFLI

WITH UNIQUE KEY CARRID CONNID.

The table object ITAB has the type hashed table, a line type corresponding to the flat structure SPFLI from the ABAP Dictionary, and a unique key with the key fields CARRID and CONNID. The internal table ITAB can be regarded as an internal template for the database table SPFLI. It is therefore particularly suitable for working with data from this database table as long as you only access it using the key.

Processing Internal Tables

When you process an internal table object, you must distinguish between the following two cases:

Operations on Entire Internal Tables

Operations on Individual Lines

Assigning Internal Tables

Like other data objects, you can use internal tables as operands in a MOVE statement

MOVE <itab1> TO <itab2>.

or the equivalent statement

<itab2> = <itab1>.

Both operands must either be compatible or convertible. These statements assign the entire contents of table <itab1> to table <itab2>, including the data in any nested internal tables. The original contents of the target table are overwritten.

If you are using internal tables with header lines, remember that the header line and the body of the table have the same name. If you want to address the body of the table in an assignment, you must place two brackets ([ ]) after the table name.

DATA: BEGIN OF line,

col1(1) TYPE c,

col2(1) TYPE c,

END OF line.

DATA: etab LIKE TABLE OF line WITH HEADER LINE,

ftab LIKE TABLE OF line.

line-col1 = 'A'. line-col2 = 'B'.

APPEND line TO etab.

MOVE etab[] TO ftab.

LOOP AT ftab INTO line.

WRITE: / line-col1, line-col2.

ENDLOOP.

The output is:

A B

The example creates two standard tables ETAB and FTAB with the line type of the structure LINE. ETAB has a header line. After filling ETAB line by line using the APPEND statement, its entire contents are assigned to FTAB. Note the brackets in the statement.

DATA: ftab TYPE SORTED TABLE OF f

WITH NON-UNIQUE KEY table_line,

itab TYPE HASHED TABLE OF i

WITH UNIQUE KEY table_line,

fl TYPE f.

DO 3 TIMES.

INSERT sy-index INTO TABLE itab.

ENDDO.

ftab = itab.

LOOP AT ftab INTO fl.

WRITE: / fl.

ENDLOOP.

The output is:

1.000000000000000E+00

2.000000000000000E+00

3.000000000000000E+00

FTAB is a sorted table with line type F and a non-unique key. ITAB is a hashed table with line type I and a unique key. The line types, and therefore the entire tables, are convertible. It is therefore possible to assign the contents of ITAB to FTAB. When you assign the unsorted table ITAB to the sorted table FTAB, the contents are automatically sorted by the key of FTAB.

In Unicode systems, the following conversion is not allowed:

DATA: BEGIN OF iline,

num TYPE i,

END OF iline,

BEGIN OF fline,

num TYPE f,

END OF fline,

itab LIKE TABLE OF iline,

ftab LIKE TABLE OF fline.

DO 3 TIMES.

iline-num = sy-index.

APPEND iline-num TO itab.

ENDDO.

ftab = itab.

loop AT ftab INTO fline.

WRITE: / fline-num.

ENDLOOP.

In a non-Unicode system, the output may look something like this:

6.03823403895813E-154

6.03969074613219E-154

6.04114745330626E-154

Here, the line types of the internal tables ITAB and FTAB are structures each with one component of type I or F. The line types are convertible, but not compatible. Therefore, when assigning ITAB to FTAB, the contents of Table ITAB are converted to type C fields and then written to FTAB. The system interprets the transferred data as type F fields, so that the results are meaningless. In Unicode systems, you are not allowed to convert numeric fields to fields of type C.

Initializing Internal Tables

initiale Speicheranforderung

Like all data objects, you can initialize internal tables with the

CLEAR <itab>.

statement. This statement restores an internal table to the state it was in immediately after you declared it. This means that the table contains no lines. However, the memory already occupied by the memory up until you cleared it remains allocated to the table.

If you are using internal tables with header lines, remember that the header line and the body of the table have the same name. If you want to address the body of the table in a comparison, you must place two brackets ([ ]) after the table name.

CLEAR <itab>[].

To ensure that the table itself has been initialized, you can use the

REFRESH <itab>.

statement. This always applies to the body of the table. As with the CLEAR statement, the memory used by the table before you initialized it remains allocated. To release the memory space, use the statement

FREE <itab>.

You can use FREE to initialize an internal table and release its memory space without first using the REFRESH or CLEAR statement. Like REFRESH, FREE works on the table body, not on the table work area. After a FREE statement, you can address the internal table again. It still occupies the amount of memory required for its header (currently 256 bytes). When you refill the table, the system has to allocate new memory space to the lines.

DATA: BEGIN OF LINE,

COL1,

COL2,

END OF LINE.

DATA ITAB LIKE TABLE OF LINE.

LINE-COL1 = 'A'. LINE-COL2 = 'B'.

APPEND LINE TO ITAB.

REFRESH ITAB.

IF ITAB IS INITIAL.

WRITE 'ITAB is empty'.

FREE ITAB.

ENDIF.

The output is:

ITAB is empty.

In this program, an internal table ITAB is filled and then initialized with REFRESH. The IF statement uses the expression ITAB IS INITIAL to find out whether ITAB is empty. If so, the memory is released.

Internal Tables as Interface Parameters

Like other data objects, you can pass internal tables by value or reference to parameter interfaces of procedures. If an internal table has a header line, you must indicate that you want to address the body of the table by placing two brackets ([ ]) after the table name.

You can define the formal parameters of the parameter interfaces of procedures as internal tables. When you do this, you can use both the predefined generic types in the TYPE addition and the generic internal table types.

To ensure compatibility with previous releases, you can also specify formal parameters in subroutines and function modules as TABLES parameters. This defines a formal parameter as a standard table with default key and header line. Whenever you pass a table without a header line as an actual parameter to a formal parameter with a header line (TABLES), the system automatically creates the corresponding header line in the routine.

Determining the Attributes of Internal Tables

To find out the attributes of an internal table at runtime that were not available statically, use the statement:

DESCRIBE TABLE <itab> [LINES <l>] [OCCURS <n>] [KIND <k>].

If you use the LINES parameter, the number of filled lines is written to the variable <lin>. If you use the OCCURS parameter, the value of the INITIAL SIZE of the table is returned to the variable <n>. If you use the KIND parameter, the table type is returned to the variable <k>: ‘T’ for standard table, ‘S’ for sorted table, and ‘H’ for hashed table.

DATA: BEGIN OF LINE,

COL1 TYPE I,

COL2 TYPE I,

END OF LINE.

DATA ITAB LIKE HASHED TABLE OF LINE WITH UNIQUE KEY COL1

INITIAL SIZE 10.

DATA: LIN TYPE I,

INI TYPE I,

KND TYPE C.

DESCRIBE TABLE ITAB LINES LIN OCCURS INI KIND KND.

WRITE: / LIN, INI, KND.

DO 1000 TIMES.

LINE-COL1 = SY-INDEX.

LINE-COL2 = SY-INDEX ** 2.

INSERT LINE INTO TABLE ITAB.

ENDDO.

DESCRIBE TABLE ITAB LINES LIN OCCURS INI KIND KND.

WRITE: / LIN, INI, KND.

The output is:

0 10 H

1,000 10 H

Here, a hashed table ITAB is created and filled. The DESCRIBE TABLE statement is processed before and after the table is filled. The current number of lines changes, but the number of initial lines cannot change.

Comparing Internal Tables

Like other data objects, you can use internal tables as operands in logical expressions.

.... <itab1> <operator> <itab2> ...

For <operator>, all operators listed in the table in Comparisons Between Data Types can be used (EQ, =, NE, <>, ><, GE, >=, LE, <=, GT, >, LT, <).

If you are using internal tables with header lines, remember that the header line and the body of the table have the same name. If you want to address the body of the table in a comparison, you must place two brackets ([ ]) after the table name.

The first criterion for comparing internal tables is the number of lines they contain. The more lines an internal table contains, the larger it is. If two internal tables contain the same number of lines, they are compared line by line, component by component. If components of the table lines are themselves internal tables, they are compared recursively. If you are testing internal tables for anything other than equality, the comparison stops when it reaches the first pair of components that are unequal, and returns the corresponding result.

DATA: BEGIN OF LINE,

COL1 TYPE I,

COL2 TYPE I,

END OF LINE.

DATA: ITAB LIKE TABLE OF LINE,

JTAB LIKE TABLE OF LINE.

DO 3 TIMES.

LINE-COL1 = SY-INDEX.

LINE-COL2 = SY-INDEX ** 2.

APPEND LINE TO ITAB.

ENDDO.

MOVE ITAB TO JTAB.

LINE-COL1 = 10. LINE-COL2 = 20.

APPEND LINE TO ITAB.

IF ITAB GT JTAB.

WRITE / 'ITAB GT JTAB'.

ENDIF.

APPEND LINE TO JTAB.

IF ITAB EQ JTAB.

WRITE / 'ITAB EQ JTAB'.

ENDIF.

LINE-COL1 = 30. LINE-COL2 = 80.

APPEND LINE TO ITAB.

IF JTAB LE ITAB.

WRITE / 'JTAB LE ITAB'.

ENDIF.

LINE-COL1 = 50. LINE-COL2 = 60.

APPEND LINE TO JTAB.

IF ITAB NE JTAB.

WRITE / 'ITAB NE JTAB'.

ENDIF.

IF ITAB LT JTAB.

WRITE / 'ITAB LT JTAB'.

ENDIF.

The output is:

ITAB GT JTAB

ITAB EQ JTAB

JTAB LE ITAB

ITAB NE JTAB

ITAB LT JTAB

This example creates two standard tables, ITAB and JTAB. ITAB is filled with 3 lines and copied to JTAB. Then, another line is appended to ITAB and the first logical expression tests whether ITAB is greater than JTAB. After appending the same line to JTAB, the second logical expression tests whether both tables are equal. Then, another line is appended to ITAB and the third logical expressions tests whether JTAB is less than or equal to ITAB. Next, another line is appended to JTAB. Its contents are unequal to the contents of the last line of ITAB. The next logical expressions test whether ITAB is not equal to JTAB. The first table field whose contents are different in ITAB and JTAB is COL1 in the last line of the table: 30 in ITAB and 50 in JTAB. Therefore, in the last logical expression, ITAB is less than JTAB.

regards

karthik

reward me points if helpfull.

Former Member · ‎04-03-2008

Hi,

Internal tables are a standard data type object which exists only during the runtime of the program. They are used to perform table calculations on subsets of database tables and for re-organising the contents of database tables according to users need.

http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb35de358411d1829f0000e829fbfe/content.htm

Difference between Work Area and Header Line

While adding or retrieving records to / from internal table we have to keep the record temporarily.

The area where this record is kept is called as work area for the internal table. The area must have the same structure as that of internal table. An internal table consists of a body and an optional header line.

Header line is a implicit work area for the internal table. It depends on how the internal table is declared that the itab will have the header line or not.

e.g.

data: begin of itab occurs 10,

ab type c,

cd type i,

end of itab. " this table will have the header line.

data: wa_itab like itab. " explicit work area for itab

data: itab1 like itab occurs 10. " table is without header line.

The header line is a field string with the same structure as a row of the body, but it can only hold a single row.

It is a buffer used to hold each record before it is added or each record as it is retrieved from the internal table. It is the default work area for the internal table

1) The difference between

whih header line and with out heater line of internal table.

ex:-

a) Data : itab like mara occurs 0 with header line.

b) Data: itab like mara occurs 0.

-While adding or retrieving records to / from internal table we have to keep the record temporarily.

-The area where this record is kept is called as work area for the internal table.

-The area must have the same structure as that of internal table. An internal table consists of a body and an optional header line.

-Header line is a implicit work area for the internal table. It depends on how the internal table is declared that the itab will have the header line or not.

a) Data : itab like mara occurs 0 with header line.

table is with header line

b) Data: itab like mara occurs 0.

table is without header line

2)work area / field string and internal table

which one is prefarable for good performance any why ?

-The header line is a field string with the same structure as a row of the body, but it can only hold a single row , whereas internal table can have more than one record.

In short u can define a workarea of an internal table which means that area must have the same structure as that of internal table and can have one record only.

Example code:

data: begin of itab occurs 10,

ab type c,

cd type i,

end of itab. " this table will have the header line.

data: wa_itab like itab. " explicit work area for itab

data: itab1 like itab occurs 10. " table is without header line.

Regards,

Harish