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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. Here is the hierarchy
Wednesday, June 16, 2010
Fields of Internal Table
SY-TABIX
Current line of an internal table. SY-TABIX is set by the statements below, but only for index tables. The field is either not set or is set to 0 for hashed tables.
APPEND sets SY-TABIX to the index of the last line of the table, that is, it contains the overall number of entries in the table.
COLLECT sets SY-TABIX to the index of the existing or inserted line in the table. If the table has the type HASHED TABLE, SY-TABIX is set to 0.
LOOP AT sets SY-TABIX to the index of the current line at the beginning of each loop lass. At the end of the loop, SY-TABIX is reset to the value that it had before entering the loop. It is set to 0 if the table has the type HASHED TABLE.
READ TABLE sets SY-TABIX to the index of the table line read. If you use a binary search, and the system does not find a line, SY-TABIX contains the total number of lines, or one more than the total number of lines. SY-INDEX is undefined if a linear search fails to return an entry.
SEARCH FOR sets SY-TABIX to the index of the table line in which the search string is found.
SY-TFILL
After the statements DESCRIBE TABLE, LOOP AT, and READ TABLE, SY-TFILL contains the number of lines in the relevant internal table.
SY-TLENG
After the statements DESCRIBE TABLE, LOOP AT, and READ TABLE, SY-TLENG contains the length of the lines in the relevant internal table.
SY-TOCCU
After the statements DESCRIBE TABLE, LOOP AT, and READ TABLE, SY-TLENG contains the initial amount of memory allocated to the relevant internal table.
Current line of an internal table. SY-TABIX is set by the statements below, but only for index tables. The field is either not set or is set to 0 for hashed tables.
APPEND sets SY-TABIX to the index of the last line of the table, that is, it contains the overall number of entries in the table.
COLLECT sets SY-TABIX to the index of the existing or inserted line in the table. If the table has the type HASHED TABLE, SY-TABIX is set to 0.
LOOP AT sets SY-TABIX to the index of the current line at the beginning of each loop lass. At the end of the loop, SY-TABIX is reset to the value that it had before entering the loop. It is set to 0 if the table has the type HASHED TABLE.
READ TABLE sets SY-TABIX to the index of the table line read. If you use a binary search, and the system does not find a line, SY-TABIX contains the total number of lines, or one more than the total number of lines. SY-INDEX is undefined if a linear search fails to return an entry.
SEARCH
SY-TFILL
After the statements DESCRIBE TABLE, LOOP AT, and READ TABLE, SY-TFILL contains the number of lines in the relevant internal table.
SY-TLENG
After the statements DESCRIBE TABLE, LOOP AT, and READ TABLE, SY-TLENG contains the length of the lines in the relevant internal table.
SY-TOCCU
After the statements DESCRIBE TABLE, LOOP AT, and READ TABLE, SY-TLENG contains the initial amount of memory allocated to the relevant internal table.
Internal Table
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.
program is .
*declaration.
data: begin of inernaltable occurs 0,
x type c,
y type i,
end of itab.
*initializing headerline
internaltable-x = 'd'.
internaltable-y = 34.
*storing value into internal table
appene internaltable .
appene internaltable .
appene internaltable .
*reading internal table
loop at itab .
write: / internaltable-x, internaltable-y. "writes to output list
endloop.
program is .
*declaration.
data: begin of inernaltable occurs 0,
x type c,
y type i,
end of itab.
*initializing headerline
internaltable-x = 'd'.
internaltable-y = 34.
*storing value into internal table
appene internaltable .
appene internaltable .
appene internaltable .
*reading internal table
loop at itab .
write: / internaltable-x, internaltable-y. "writes to output list
endloop.
what is abap
ABAP (Advanced Business Application Programming, originally Allgemeiner Berichts-Aufbereitungs-Prozessor, German for "general report creation processor" [citation needed]) is a very high level programming language created by the German software company SAP. It is currently positioned, alongside the more recently introduced Java, as the language for programming SAP's Web Application Server, part of its NetWeaver platform for building business applications. Its syntax is somewhat similar to COBOL.
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