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.
Self-Test Question
We need to download an internal table to the Presentation Server (local workstation). Whenever we run the program, the same file has to be saved as a separate file in sequential order. Ex: 0001.txt, 0002.txt etc. Where can we store the last file number?
SAP has a table TVARV for storing the variants.
A record may be created in TVARV for all the programs that require these kind of incremental records. For Ex: the record could be 010ZBC_TEST MM sequence rec where first part consists of client code and the program being run. Client code is required because TVARV does not have a field for client code. The second part is the description indicating the purpose what the record is created. This entire string may be posted in the Name field (char - 30).
The Type field (char- 1) may be populated with P or S (Parameter or Selection).
Low field (char- 45) may be populated with '0001' when run first time and increment it by one in your program for downloading of the internal table.
