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We will use the same setting as in Tutorial: Simple Query Processing. So you should follow steps 1-4.
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After translating the following output will be displayed. You can see, that only the selected attributes are printed.
Although, the examples only contain one operator, the operators can be connected. E.g. first a selection and than a projection:
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selected = SELECT({predicate='seller=1 || seller=2'}, nexmark:auction)
out = PROJECT({ATTRIBUTES=['id', 'initialbid', 'seller']},selected) |
Map
PROJECT only allow the selection of attributes. With the MAP-Operator calculations can be done on the input. The simpliest calculation is the output of an input attribute, so Map is more general than Project. (Warning: You should not use Map instead of Project, because it requires more processing capabilties).
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