internal tables

[Former Member]

can somebody explain me how many types of internal tables are ther along with how do we declare them plz...

[Former Member]

Check this link.

http://help.sap.com/saphelp_erp2005vp/helpdata/en/fc/eb35de358411d1829f0000e829fbfe/content.htm

[former_member156446]

Hi Vinay

Standard Internal Tables

Standard tables have a linear index. You can access them using either the index or the key. If you use the key, the response time is in linear relationship to the number of table entries. The key of a standard table is always non-unique, and you may not include any specification for the uniqueness in the table definition.

This table type is particularly appropriate if you want to address individual table entries using the index. This is the quickest way to access table entries. To fill a standard table, append lines using the (APPEND) statement. You should read, modify and delete lines by referring to the index (INDEX option with the relevant ABAP command). The response time for accessing a standard table is in linear relation to the number of table entries. If you need to use key access, standard tables are appropriate if you can fill and process the table in separate steps. For example, you can fill a standard table by appending records and then sort it. If you then use key access with the binary search option (BINARY), the response time is in logarithmic relation to

the number of table entries.

Sorted Internal Tables

Sorted tables are always saved correctly sorted by key. They also have a linear key, and, like standard tables, you can access them using either the table index or the key. When you use the key, the response time is in logarithmic relationship 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, and you must specify either UNIQUE or NON-UNIQUE in the table definition. Standard tables and sorted tables both belong to the generic group index tables.

This table type is particularly suitable if you want the table to be sorted while you are still adding entries to it. You fill the table using the (INSERT) statement, according to the sort sequence defined in the table key. Table entries that do not fit are recognised before they are inserted. The response time for access using the key is in logarithmic relation to the number of

table entries, since the system automatically uses a binary search. Sorted tables are appropriate for partially sequential processing in a LOOP, as long as the WHERE condition contains the beginning of the table key.

Hashed Internal Tables

Hashes tables have no internal linear index. You can only access hashed tables by specifying the key. The response time is constant, regardless of the number of table entries, since the search uses a hash algorithm. The key of a hashed table must be unique, and you must specify UNIQUE in the table definition.

This table type is particularly suitable if you want mainly to use key access for table entries. You cannot access hashed tables using the index. When you use key access, the response time remains constant, regardless of the number of table entries. As with database tables, the key of a hashed table is always unique. Hashed tables are therefore a useful way of constructing and

using internal tables that are similar to database tables.

Index Tables

Index table is only used to specify the type of generic parameters in a FORM or FUNCTION. That means that you can't create a table of type INDEX.

Internal tables are not DB tables. Standard and Sorted tables in combined are basically called as Index tables and there nothing else.

[Former Member]

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.

Special Features of Standard Tables

Unlike sorted tables, hashed tables, and key access to internal tables, which were only introduced in Release 4.0, standard tables already existed several releases previously. Defining a line type, table type, and tables without a header line have only been possible since Release 3.0. For this reason, there are certain features of standard tables that still exist for compatibility reasons.

Standard Tables Before Release 3.0

Before Release 3.0, internal tables all had header lines and a flat-structured line type. There were no independent table types. You could only create a table object using the OCCURS addition in the DATA statement, followed by a declaration of a flat structure:

DATA: BEGIN OF <itab> OCCURS <n>,

...

<fi> ...

...

END OF <itab>.

This statement declared an internal table <itab> with the line type defined following the OCCURS addition. Furthermore, all internal tables had header lines.

The number <n> in the OCCURS addition had the same meaning as in the INITIAL SIZE addition from Release 4.0. Entering ‘0’ had the same effect as omitting the INITIAL SIZE addition. In this case, the initial size of the table is determined by the system.

The above statement is still possible in Release 4.0, and has roughly the same function as the following statements:

TYPES: BEGIN OF <itab>,

...

<fi> ...,

...

END OF <itab>.

DATA <itab> TYPE STANDARD TABLE OF <itab>

WITH NON-UNIQUE DEFAULT KEY

INITIAL SIZE <n>

WITH HEADER LINE.

In the original statement, no independent data type <itab> is created. Instead, the line type only exists as an attribute of the data object <itab>.

Standard Tables From Release 3.0

Since Release 3.0, it has been possible to create table types using

TYPES <t> TYPE|LIKE <linetype> OCCURS <n>.

and table objects using

DATA <itab> TYPE|LIKE <linetype> OCCURS <n> [WITH HEADER LINE].

The effect of the OCCURS addition is to construct a standard table with the data type <linetype>. The line type can be any data type. The number <n> in the OCCURS addition has the same meaning as before Release 3.0. Before Release 4.0, the key of an internal table was always the default key, that is, all non-numeric fields that were not themselves internal tables.

The above statements are still possible in Release 4.0, and have the same function as the following statements:

TYPES|DATA <itab> TYPE|LIKE STANDARD TABLE OF <linetype>

WITH NON-UNIQUE DEFAULT KEY

INITIAL SIZE <n>

[WITH HEADER LINE].

They can also be replaced by the following statements:

Standard Tables From Release 4.0

When you create a standard table, you can use the following forms of the TYPES and DATA statements. The addition INITIAL SIZE is also possible in all of the statements. The addition WITH HEADER LINE is possible in the DATA statement.

Standard Table Types

Generic Standard Table Type:

TYPES <itab> TYPE|LIKE [STANDARD] TABLE OF <linetype>.

The table key is not defined.

Fully-Specified Standard Table Type:

TYPES <itab> TYPE|LIKE [STANDARD] TABLE OF <linetype>

WITH [NON-UNIQUE] <key>.

The key of a fully-specified standard table is always non-unique.

Standard Table Objects

Short Forms of the DATA Statement :

DATA <itab> TYPE|LIKE [STANDARD] TABLE OF <linetype>.

DATA <itab> TYPE|LIKE [STANDARD] TABLE OF <linetype>

WITH DEFAULT KEY.

Both of these DATA statements are automatically completed by the system as follows:

DATA <itab> TYPE|LIKE STANDARD TABLE OF <linetype>

WITH NON-UNIQUE DEFAULT KEY.

The purpose of the shortened forms of the DATA statement is to keep the declaration of standard tables, which are compatible with internal tables from previous releases, as simple as possible. When you declare a standard table with reference to the above type, the system automatically adopts the default key as the table key.

Fully-Specified Standard Tables:

DATA <itab> TYPE|LIKE [STANDARD] TABLE OF <linetype>

WITH [NON-UNIQUE] <key>.

The key of a standard table is always non-unique.

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.

plz reward if useful

vivek

[Former Member]

Hi,

Internal tables are the core of ABAP. They are like soul of a body. For any program we use

internal tables extensively. We can use Internal tables like normal data base tables only, but the

basic difference is the memory allocated for internal tables is temporary. Once the program is

closed the memory allocated for internal tables will also be out of memory.

But while using the internal tables, there are many performance issues to be considered. i.e which

type of internal table to be used for the program..like standard internal table, hashed internal

table or sorted internal table etc..

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.

Standard Internal Tables

Standard tables have a linear index. You can access them using either the index or the key. If you use the key, the response time is in linear relationship to the number of table entries. The key of a standard table is always non-unique, and you may not include any specification for the uniqueness in the table definition.

This table type is particularly appropriate if you want to address individual table entries using the index. This is the quickest way to access table entries. To fill a standard table, append lines using the (APPEND) statement. You should read, modify and delete lines by referring to the index (INDEX option with the relevant ABAP command). The response time for accessing a standard table is in linear relation to the number of table entries. If you need to use key access, standard tables are appropriate if you can fill and process the table in separate steps. For example, you can fill a standard table by appending records and then sort it. If you then use key access with the binary search option (BINARY), the response time is in logarithmic relation to

the number of table entries.

Sorted Internal Tables

Sorted tables are always saved correctly sorted by key. They also have a linear key, and, like standard tables, you can access them using either the table index or the key. When you use the key, the response time is in logarithmic relationship 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, and you must specify either UNIQUE or NON-UNIQUE in the table definition. Standard tables and sorted tables both belong to the generic group index tables.

This table type is particularly suitable if you want the table to be sorted while you are still adding entries to it. You fill the table using the (INSERT) statement, according to the sort sequence defined in the table key. Table entries that do not fit are recognised before they are inserted. The response time for access using the key is in logarithmic relation to the number of

table entries, since the system automatically uses a binary search. Sorted tables are appropriate for partially sequential processing in a LOOP, as long as the WHERE condition contains the beginning of the table key.

Hashed Internal Tables

Hashes tables have no internal linear index. You can only access hashed tables by specifying the key. The response time is constant, regardless of the number of table entries, since the search uses a hash algorithm. The key of a hashed table must be unique, and you must specify UNIQUE in the table definition.

This table type is particularly suitable if you want mainly to use key access for table entries. You cannot access hashed tables using the index. When you use key access, the response time remains constant, regardless of the number of table entries. As with database tables, the key of a hashed table is always unique. Hashed tables are therefore a useful way of constructing and

using internal tables that are similar to database tables.

Index Tables

Index table is only used to specify the type of generic parameters in a FORM or FUNCTION. That means that you can't create a table of type INDEX.

Internal tables are not DB tables. Standard and Sorted tables in combined are basically called as Index tables and there nothing else.

REWARD IF USEFUL

GAURAV J.