SQL supports a set of predefined domains. Perform selection using the predicate P. Project out the attributes 1-n. Use distinct to remove duplicates. Uses keyword as. Two relations have same attribute names.
Result attributes is derived.
Need tuple variables. Use order by for the attribute on which you want to sort. By default, set operations remove duplicates. If all is specified, then duplicates are retained. Aggregates Can be used as result field or operand in a where clause.