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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.

Other versions: 7.31 | 7.40 | 7.54

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.