Varunion

Combines contents of two or more relations with similar schemas.

Usage

varunion ((rel1, rel2, ...) : unioned-data)

Details

Returns all tuples from the set that represents the combination of relations.

Notes

If relations do not have the same schema, 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
      RELATION books3: title char, author char, pub_date date, pages number
      Title9|Author9|01-02-2003|123

when executing the plan:

      PLAN test
      {
       INPUT: stream books1, stream books2, stream books3
       OUTPUT: stream answer
      
       BODY
       {
         varunion ((books1, books2, books3) : answer)
       }
      }

will generate the following output:

      ----------------------------------------------
      RELATION: test_answer
      attrs: title, author, pub_date, pages
      ----------------------------------------------
      Title2|Author2|12-23-1954|479
      Title4|Author3|01-01-1968|32
      Title1|Author1|09-01-1991|34
      Title3|Author2|05-09-2002|733
      Title5|Author2|07-03-2001|1152
      Title6|Author4|03-14-1977|168
      Title7|Author4|07-23-1999|332
      Title9|Author9|01-02-2003|123
      ----------------------------------------------