Internal Table Doubt!!!

Question

Hi!
   I ve doubt on the following,
1) Data: Begin of itab occurs 10
              ......, end of itab.
    In the above what will happen if i store records more than 10 & less than 10 records
if more than 10 where records will be stored .
if i store 5 then whats the remaining storage space.
2)  Types of internal Table
     SOrted, Hashed, index, standard
    Can u pls explain  in short terms(i dont want big details) good understanding
     which one from above improve performance
3)  see this,
     types: begin of ty_itab occurs 0,
               mara like mara-matnr.
               end of ty_itab,
               ty_t_itab type standard table of ty_itab with default key.
Data:  it_itab type ty_t_itab.
          it_itab2 like it_itab
          or it_itab2 type ty_t_itab.
  i want to know,
      ty_t_itab is an internal table with header line or not
     it_itab, it_itab2 has header line or not
  Pls reply guys, looking for your reply.
Thanks  In Advance.
Rahul.

Answer 1

Hi,
<b>if more then 10 then records will be stored in the table itself
if less than 10 then space willbe reserved for 10 records</b>
<b>Standard Tables:</b>
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.
<b>Sorted Tables:</b>
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.
<b>Hashed Tables:</b>
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.
<b>it_itab, it_itab2 has header line</b>
Regards,
ravish
plz dont forget to reward points if useful