Data Dictionary

Definition of Foreign Keys  Relationships between tables are represented in the ABAP Dictionary by foreign keys  A foreign key is a field (or combination of fields) that represents the primary key of another table

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Foreign Key Relationships | 1.03 | September-2003

Uses of Foreign Keys • • •

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Maintain data integrity Provide help texts Create aggregate dictionary objects

Foreign Key Relationships | 1.03 | September-2003

Prerequisites for Constructing Foreign Key Relationships • •

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The foreign key field and the primary key of the check table must share the same domain A value table must exist for that domain

Foreign Key Relationships | 1.03 | September-2003

Foreign Keys: Key Terminology Value Table

Check Table

Foreign Key Table Slide 4

Foreign Key Relationships | 1.03 | September-2003

 The table containing the set of allowed values attached to a domain

 The table that is referenced by a foreign key

 The table containing fields that are the primary key of the other table

Foreign Key Terminology: Check Table = Value Table  In many cases, the value table and the check table will be the same

Check Table

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Foreign Key Relationships | 1.03 | September-2003

Valu e Tabl e

Foreign Key Terminology: Check Table ≠ Value Table  Sometimes check table is another table containing a subset of the records in a value table.

Check Table

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Foreign Key Relationships | 1.03 | September-2003

Valu e Tabl e

Establishing a Foreign Key Relationship in the ABAP Dictionary  During defining Foreign Key Relationship, system suggests a Foreign Key Relationship for you.

Data Dictionary

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Foreign Key Relationships | 1.03 | September-2003

Cardinality  When creating foreign key relationships, you should always specify the cardinality of that relationship

n : m 1

1

C

C N CN

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Foreign Key Relationships | 1.03 | September-2003

Creating a Foreign Key Relationship

Foreign key push-button

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Foreign Key Relationships | 1.03 | September-2003

Maintaining a Foreign Key Relationship’s Attributes

Enter a description (short text). Check table

Maintain foreign key type

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Foreign Key Relationships | 1.03 | September-2003

Maintain cardinality n : m

Foreign Keys with Multiple Fields  If the primary key of a check table has multiple fields (i.e. it has a composite primary key), some type of assignment must be made for each field when creating a foreign key relationship.

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Foreign Key Relationships | 1.03 | September-2003

Field-By-Field Assignment  When performing a field-by-field assignment, all key fields in the check table are used to determine valid entries in the foreign key table.

Foreign Key Table

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Foreign Key Relationships | 1.03 | September-2003

Check Table

Partial Foreign Keys  When creating a partial foreign key, certain fields are flagged as generic  These fields are ignored by the system when validating records that are inserted into the foreign key table.

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Foreign Key Relationships | 1.03 | September-2003

Constant Foreign Keys  When creating a constant foreign key, certain fields are assigned a literal value  Only records in the check table with that value in the corresponding field are used to determine whether records in the foreign key table are valid.

” O I B “

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Foreign Key Relationships | 1.03 | September-2003

Combined use of Partial and Constant foreign keys

Generic foreign key Constant foreign key

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Foreign Key Relationships | 1.03 | September-2003

Including Structures in Tables  Structure is a group of internal fields that logically belong together

Substructures

SAP Tables Customizing Includes

Table YCUSTAB .INCLUDE YSTRUC

Table XYZ .INCLUDE CI_XXX

Customer Tables

Append Structures Field 1 Field 2 ... Field n

Table T .APPEND

ZAT

SAP Tables

Including Structures in Tables (Continued..) Customer Tables Substructures Table YCUSTAB .INCLUDE

YSTRUC

SAP Tables Customizing Includes Table XYZ .INCLUDE

CI_XXX

Append Structures Field 1 Field 2 ... Field n

Table T .APPEND

ZAT

SAP Tables

Substructure YS Table Field YT1 S1 (TRANSP) S2 .INCLUDE

YS-F1 YS-F2 YS-F3...

Data element

YS

F1 Table Field YT2 S1 (TRANSP) S2 .INCLUDE F1

Data element

YS

Customizing Include CI_XXX CI_XXX-F1CI_XXX-F2CI_XXXF3 Table Table

Field Field

XYZ XYZ

S1 S1 F1 F1 .. .. .. Fn Fn .INCLUDE

Data Data element element

CI_XXX

Append Structure ZAT

Table

Field

T

S1 F1 ... Fn .APPEND

ZAT-F1 ZAT-F2 ZAT-F3

Data element

ZAT