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The Relational Database Dictionary, Extended Edition by C. J. Date

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Chapter 21. T

table 1. SQL analog of either a relation or a relvar, as the context demands. Here are some of the major differences between tables in SQL and their relational counterparts: (a) SQL tables can contain duplicate rows; (b) SQL tables can contain nulls; (c) SQL tables have a left-to-right column sequence; (d) SQL tables can have two or more columns with the same name; (e) SQL tables can have what are, in effect, columns with no name at all. 2. More generally, a picture of a relation (on paper, for example). Note: Confusion between relations and such tabular pictures probably accounts for the popular misconception that relations are "flat" or two-dimensional. While it's obviously true that those pictures are two-dimensional, relations ...

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