در زیر تعریف دو واژه که خیلی در طراحی و پیاده سازی پایگاه داده به کار میره و بعضی از برنامه نویسان تعریفی دقیقی از اون ها نمیدونن آورده شده:
Viewpoint: Relational theory
Name: Relation
Definition:
This term is seldom used by nonacademics, but some theory literature uses this term exclusively to mean what most programmers think of as a table. It consists of rows and columns, with no duplicate rows. There is absolutely no ordering implied in the structure of the relation, neither for rows nor for columns.
Note:Relational databases take their name from this term;the name does not come from the fact that tables can be related.
Viewpoint: Implementation
Name: Table
Definition:
The term table is almost the same as a relation. It is a particularly horrible name, because the structure that this list of terms is in is also referred to as a table. These tables,much like the Excel tables, have order. It cannot be reiterated enough that tables have no order.
Another concern is that a table may technically have duplicate rows. It is up to you as the developer to apply constraints to make certain that duplicate rows are not allowed.
Tables also have another usage, in that the results of a query (including the intermediate results that occur as a query is processing multiple joins and the other clauses of a query) are also called tables, and the columns in these intermediate tables may not even have column names.
Note:This one naming issue causes more problems for new SQL programmers than any other.
منبع: کتاب Pro SQL Server 2008 Relational Database Design and Implementation انتشارات APress فصل 1 صفحه 10.
