The Relational Database Dictionary

Chapter 1. The Dictionary

Table 1-1. 

0-adic	Niladic.
0-tuple	The empty tuple.
1NF	First normal form.
2NF	Second normal form.
2VL	Two-valued logic.
3NF	Third normal form.
3VL	Three-valued logic.
4NF	Fourth normal form.
5NF	Fifth normal form.
6NF	Sixth normal form.

A

A relationally complete, “reduced instruction set” version of relational algebra with only two operators—REMOVE (essentially projection over all attributes but one) and an algebraic analog of either NAND or NOR, q.v. The name is a doubly recursive acronym: it stands for ALGEBRA, which in turn stands for A Logical Genesis Explains Basic Relational Algebra. As this expanded name suggests, it is designed in such a way as to emphasize its close relationship to, and solid foundation in, the discipline of predicate logic, q.v.

ad hoc polymorphism

Overloading.

aggregate operator

A read-only operator that derives a single value (typically but not necessarily scalar) from the set or bag of values appearing as values of some attribute of some relation. Contrast summary. Note: If (a) the argument to some aggregate operator invocation is empty, and (b) that aggregate operator is essentially just shorthand for repeated invocation of some scalar operator (e.g., the scalar operator is “+” in the case of the aggregate operator SUM), and (c) an identity value exists for that scalar operator (the identity value is 0 in the case of “+”), then the result of that invocation is that identity value. ...