Database Reference
In-Depth Information
As with selection, brackets may be used to avoid ambiguity. Ullman's notation has
been omitted here; though slightly different in syntax, its result is similar.
Examples 9:
The following examples illustrate the use of renaming and relational
assignment:
7.5 Other Operators
Other operations to facilitate computation usually exist. A brief summary of some of the
common additional operators is provided here (based on Date's notation). These will be
further clarified, once the student is exposed to a DSL such as SQL (which we will discuss
later in the course).
Extend:
The
EXTEND
operator takes a relation as input, and returns a replica of it
with one additional column (attribute), as defined by the user. The BNF notation for the
syntax is
Example 10:
List courses in program “BSC1”, with an additional descriptive column
