The keyword “distinct” can optionally appear in the select clause of an SQL query. If it exists, the query processor should remove duplicates from the output table. (a) Revise the SQL grammar of Fig....

The keyword “distinct” can optionally appear in the select clause of an SQL query. If it exists, the query processor should remove duplicates from the output table.

(a) Revise the SQL grammar of Fig. 9.7 to include the distinct keyword.

(b) Revise the SimpleDB lexical analyzer and query parser to implement your syntax changes.

(c) Revise the basic query planner to generate an appropriate nodups operation for select distinct queries.