The kind of operations needed in a table-at-a-time language were introduced in the
form of relational algebra in Chapter 17. For tutorial purposes, relational algebra has
the advantages that fundamental operations such as selecting rows, selecting columns
and joining tables are expressed explicitly as separate statements. Relational algebra
also complies with the requirements of the relational model. In practice, the table-at-a-
time language provided with almost all relational database management systems is the
SQL (pronounced ess-cue-ell) language, which combines row, column and join
operations into a single statement ...
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