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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.
- 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.