Referential integrity

Each circle is implemented by a set of tables in a relational database model (Date, 2003). Referential integrity constraints are used within each circle and between circles to ensure consistency of the event information. Triggers and constraints are used within each circle to facilitate data insertion and removal. There are no cross-circle constraints and triggers due to the unequal relationship between these two circles. 

Referential integrity between work order and maintenance task schedule/plan... 

Screen input formatting and input verification, data recovery, referential integrity, data transfers, print controls... 

Record locking to prevent parallel access, security to prevent inadvertent or malicious modification, disaster recovery, maintenance of referential integrity... 

System failure during read/write operations Data retention following system failure Cyclical file management Prevention of duplicate record creation Referential integrity Impact on existing modules Regression testing... 

The column pubchem.substance.cid associations is taken directly from the sdf files supplied by PubChem. It has all the necessary information, but it is not in a proper form for a relation between pubchem.substance and pubchem.compounds. This is because too much information has been crammed into this column. For example, the cid associations for substance id 22 contains the data "449653 1449655 2 6540406 2". This means that there are three compound ids associated with this substance id. In other words, there is a many-to-many relationship between compounds and substances. While it would be possible to parse the cid associations column when the compound id is needed, it is better to have a clear relationship between substance ids and compounds ids. It is better because it enforces and preserves the relational integrity (or referential integrity) between these data. It also makes selecting data from all three data sources quicker and easier. 

MODEL Referential Integrity Device Format Communication Line Technical Interface Technical Cycle Action... 

The management of patients whose identity is genuinely unknown Compromised database keys or referential integrity issues Functionality and procedures for merging duplicated patient records Preservation of identity during data migration and database merging... 

In practice, corruption of clinical data is often more subtle than a simple scrambling of text. One potential failure mode which can give rise to corruption is the loss of referential integrity within the database. Most proprietary databases hold information in tables, collections of data with a conunon set of fields and sanantic meaning in the real world. Information in one table is often linked to that in another and it is this linkage which is vulnerable. 

Referential integrity The requirement that when a reference is made to a data item, that data item must exist. 

Referential Integrity Constraint If a relation has a designated attribute (or a concatenation thereof) which acts as a foreign key with which the relation refers to another, then the value of the foreign key in the referring relation must be a primary key value in the referred relation. 

Figure 6 shows how the schema illustrated in Fig. 1 can be declared in SQL. Notice that SQL includes constructs to declare integrity constraints (e.g., a referential integrity on from DNA sequence to organism) and even an action to be performed if it is violated (e.g., cascading deletions, by deleting every referring tuple when a referenced tuple is deleted). 

SQL can also express insertions, deletions and updates, as indicated in Fig. 7. Note in Fig. 7 that on insertion it is possible to omit null values by listing only the attributes for which values are being supplied. Note also that the order of insertion in Fig. 7 matters, since referential integrity constraints would otherwise be violated. Finally, note that, because of cascading deletions, the final statement will also delete all tuples in DNA sequence that refer to the primary key of the tuple being explicitly deleted in organism. 

Note how ODL allows inverse relationships to be named, as a consequence of which referential integrity is enforced in both directions. 

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