Database Reference
In-Depth Information
Rantzau, R., & Mangold, C. (2006). Laws for rewriting queries containing division operators. In the
Proceedings of IEEE ICDE
.
XAMPP. (2010). An apache distribution containing MySQL. Retrieved June 2010, from http://www.
apachefriends.org/en/xampp.html
KEY TERMS AND DEFINITIONS
Relational Algebra (RA):
an offshoot of first-order logic (and of algebra of sets), deals with a set
of finitary relations which is closed under certain operators. These operators operate on one or more
relations to yield a relation.
Structured Query Language (SQL):
a database computer language designed for managing data
in relational database management systems (RDBMS), and originally based upon relational algebra.
MySQL:
a relational database management system (RDBMS) that runs as a server providing multi-
user access to a number of databases.
Divide Operator:
Relational division is one of the eight basic operations in relational algebra. Though
it can be coded using four of the five core relational algebra operators, it has been defined as standalone
operator to make the coding of queries involving explicit division easier. The concept is that a divisor
relation is used to partition a dividend relation and produce a quotient or results table. The quotient table
is made up of those values of one group of columns (or a single column) for which a second group of
columns (or column) had all of the values in the divisor.
Zql:
An established SQL lexical parser to check and validate ordinary SQL queries and to explode
clauses such as
select
,
from
and
where
.
XAMPP:
an Apache distribution which contains MySQL - a popular DBMS which is free, wide-
spread and easy to install.
Grammar:
a set of rules or standards that specifiy the query language.
ENDNOTE
1
The result differed only when division by an empty set occurred.
