Minus

Subtracts one relation from another.

Usage

minus (lhs, rhs : minused-data)

Details

Returns all tuples from the set that represents the subtraction of lhs and rhs.

Notes

If relations do not have the same schemas, errors will occur.
By definition, sets are composed of unique elements - thus, duplicates will not be returned.

Known Bugs

None.

Example

Using the input:

      RELATION books1: title char, author char, pub_date date, pages number
      Title1|Author1|09-01-1991|34
      Title2|Author2|12-23-1954|479
      Title3|Author2|05-09-2002|733
      Title4|Author3|01-01-1968|32
      Title5|Author2|07-03-2001|1152
      RELATION books2: title char, author char, pub_date date, pages number
      Title3|Author2|05-09-2002|733
      Title4|Author3|01-01-1968|32
      Title6|Author4|03-14-1977|168
      Title7|Author4|07-23-1999|332

when executing the plan:

      PLAN test
      {
       INPUT: stream books1, stream books2
       OUTPUT: stream answer
      
       BODY
       {
         minus (books1, books2 : answer)
       }
      }

will generate the following output:

      ----------------------------------------------
      RELATION: test_answer
         attrs: title, author, pub_date, pages
      ----------------------------------------------
      Title2|Author2|12-23-1954|479
      Title1|Author1|09-01-1991|34
      Title5|Author2|07-03-2001|1152
      ----------------------------------------------