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Monday, June 18, 2007

Internal Tables and Types


Key access to a standard table uses a linear search. This means that the time required
for a search is in linear relation to the number of table entries.

You should use index operations to access standard tables.

SORTED table

Defines the table as one that is always saved correctly sorted.

Key access to a sorted table uses a binary key. If the key is not unique, the system takes
the entry with the lowest index. The runtime required for key access is logarithmically
related to the number of table entries.

HASHED table

Defines the table as one that is managed with an internal hash procedure

You can only access a hashed table using the generic key operations or other generic
operations ( SORT, LOOP, and so on). Explicit or implicit index operations (such as
LOOP ... FROM oe INSERT itab within a LOOP) are not allowed.

INDEX table

A table that can be accessed using an index.

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.

Standard tables and sorted tables are index tables.

Syntax :
DATA itab TYPE table type of line type [WITH UNIQUE/NON-UNIQUE KEY ]
[Iinitial size n] [WITH HEADER LINE]

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