Duplicate Unique Keys - ABAP Keyword Documentation

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Duplicate Unique Keys

When rows are inserted into internal tables with a unique primary key or unique secondary key, duplicates can occur with respect to one or more of these keys. Depending on whether the insert takes place as a single record operation or a mass operation, the ABAP runtime environment responds as follows to an attempt to insert an entry with duplicate key values:

First, it checks whether duplicate key values would occur with respect to the primary key. The system behavior is as follows depending on the operation:

When single rows are inserted using the variant

INSERT wa INTO TABLE itab

duplicate with respect to the primary key are ignored and sy-subrc is set to 4. This is often used to filter out duplicates when the table is constructed.

In all other cases, such as

INSERT ... INTO itab INDEX idx
INSERT LINES OF (mass operation)
APPEND
COLLECT
=, IMPORT (mass operations)

the runtime error ITAB_DUPLICATE_KEY occurs.

A check is then made to see whether duplicate key values would occur with respect to any existing unique secondary keys. If this is the case,

an exception of the class CX_SY_ITAB_DUPLICATE_KEY is raised for the statements INSERT and APPEND, if the operation is a single record operation.

For all other insert and assignment operations, particularly for all mass operations, the runtime error ITAB_DUPLICATE_KEY occurs.

Example

The first INSERT statement does not insert a line and sets sy-subrc to the value 4. The second INSERT statement produces a runtime error.

DATA itab TYPE SORTED TABLE OF i WITH UNIQUE KEY table_line.

itab = VALUE #( ( 1 ) ( 2 ) ( 3 ) ).

INSERT 2 INTO TABLE itab.

INSERT 2 INTO itab INDEX 2.