Internal table and work area

Question

Hi,
       can anybody explain the concepts of Internal table and work area.Thanks in advance.

Answer 1

hai,
This may help u.
WORKAREA is a structure that can hold only one record at a time. It is a collection of fields. We use workarea as we cannot directly read from a table. In order to interact with a table we need workarea. When a Select Statement is executed on a table then the first record is read and put into the header of the table and from there put into the header or the workarea(of the same structure as that of the table)of the internal table and then transferred top the body of the internal table or directly displayed from the workarea.
Each row in a table is a record and each column is a field.
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.
Internal tables are used for storing records which are obtained as a result when we use select statement on database. internal tables are run time entities and doesn't occupy any memory. they are dynamic.
internal tables are of types.
1. internal tables with header line. [header and body]
2. internal tables with out header line. [only body]
Workarea is the concept which is mainly useful when working with internal tables with out header line.
at any point of time we can access only one record through header of a internal table. every thing should be done [inserting,modifying, reading ] through header only.
ex: data: itab like standard table of mara with header line.
for internal tables with out header line we will create a work area [explicit header] as type of table for storing data into internal table.
ex: data: itab like mara,
wa like mara.
more about internal table types:
Standard table:
The key access to a standard table uses a sequential search. The time required for an access is linearly dependent on the number of entries in the internal table.
You should usually access a standard table with index operations.
Sorted table:
The table is always stored internally sorted by its key. Key access to a sorted table can therefore use a binary search. If the key is not unique, the entry with the lowest index is accessed. The time required for an access is logarithmically dependent on the number of entries in the internal table.
Index accesses to sorted tables are also allowed. You should usually access a sorted table using its key.
Hash table:
The table is internally managed with a hash procedure. All the entries must have a unique key. The time required for a key access is constant, that is it does not depend on the number of entries in the internal table.
You cannot access a hash table with an index. Accesses must use generic key operations (SORT, LOOP, etc.).
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.
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.
DATA ITAB TYPE HASHED TABLE OF SPFLI
WITH UNIQUE KEY CARRID CONNID.
with regards,
B.Sowjanya,
reward points if helpful.