deletion anomaly
occurs when you delete a record that may contain attributes that shouldn’t be deleted
A deletion anomaly occurs when you delete a record that may contain attributes that shouldn’t be deleted.
functional dependency (FD)
describes how individual attributes are related
One important theory developed for the entity relational (ER) model involves the notion of functional dependency (FD).
insertion anomaly
occurs when you are inserting inconsistent information into a table
An insertion anomaly occurs when you are inserting inconsistent information into a table.
join
used when you need to obtain information based on two related tables
However, redundancy can sometimes lead to performance improvements; for example, when redundancy can be used in place of a join to connect data.
update anomaly
changing existing information incorrectly
Changing existing information incorrectly is called an update anomaly.
Armstrong’s axioms
a set of inference rules used to infer all the functional dependencies on a relational database
Armstrong’s axioms are a set of inference rules used to infer all the functional dependencies on a relational database.
DBA
database administrator
Some database administrators (DBA) might choose to keep these tables separated for a couple of reasons.
decomposition
a rule that suggests if you have a table that appears to contain two entities that are determined by the same PK, consider breaking them up into two tables
Decomposition is the reverse of the Union rule.
dependent
the right side of the functional dependency diagram
The left side of the above FD diagram is called the determinant, and the right side is the dependent.
determinant
the left side of the functional dependency diagram
The left side of the above FD diagram is called the determinant, and the right side is the dependent.
functional dependency (FD)
a relationship between two attributes, typically between the PK and other non-key attributes within a table
A functional dependency (FD) is a relationship between two attributes, typically between the PK and other non-key attributes within a table.
non-normalized table
a table that has data redundancy in it
A dependency diagram, shown in Figure 11.6, illustrates the various dependencies that might exist in a non-normalized table.
Union
a rule that suggests that if two tables are separate, and the PK is the same, consider putting them together
By the Union rule, if X → Y and X → Z, then X → YZ.
These terms were extracted from Database Design – 2nd Edition by Adrienne Watt, eCampusOntario (originally published by BCcampus) which is licensed under a Creative Commons Attribution 4.0 International License. Chapter text adapted from Relational Design Theory by Nguyen Kim Anh, licensed under CC BY 3.0.