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ABAP Keyword Documentation → ABAP Programming Guidelines → Robust ABAP →Internal Tables
An internal table is a dynamic data object consisting of a sequence of rows with the same data type. The data type of an internal table is a table type that has the following basic properties of every internal table:
Internal tables enable variable datasets (a variable number of rows) with a fixed structure (the row type) to be edited in the working memory of the internal session of a program. The content of an internal table can either be accessed sequentially in a LOOP or by accessing inidividual rows (for example, by using READ TABLE or a table expression).
There are two ways of accessing individual rows:
Primary table access is possible for all three table categories. Access using the primary key, however, is optimized only for sorted tables and hashed tables. In standard tables, primary key access uses a linear search. Access using the primary row index, on the other hand, is possible for standard tables and sorted tables only. As well as its primary key, an internal key can also have further secondary keys. These keys enhance and optimize access options to the various table categories.