types of internal tables

[Former Member]

hi

In which cases we will use standard internal tables ,

in which cases we will use sorted internal tables,

In which cases we will use hashed internal tables ,

that is where we will use these internal tables seperately.

what is meant by hashed internal table

[ferry_lianto]

Hi,

There are 3 types of Internal tables.

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.

Regards,

Ferry Lianto

Please reward points if helpful.

[Former Member]

hi jyothsna

<b>Standard tables</b> have an internal <i>linear index</i>. 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.

<b>Sorted tables</b> 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 <i>binary search</i>. 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 NON-UNIQUE. Standard tables and sorted tables are known generically as index tables.

<b>Hashed tables</b> have no linear index. You can only access a <i>hashed table</i> 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.

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[Former Member]

Hi,

Refer following details:

<b>Internal Tables as Data Types</b>

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.

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.

Jogdand M B

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[Former Member]

Hi

Please refer to the below link,

You can read more about your query:

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

Thanks,

Janani

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[Former Member]

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