single

single(T.‘a) 🡒 ‘a, aggregator

The aggregator fails if any group has more than one element.

Example:

table T = with
  [| as A, as B |]
  [| 0,   "a"   |]
  [| 1,   "b"   |]
  [| 1,   "c"   |]

table G[gdim] = by T.B

where T.B != "c"
  show table "" a1b4 with
    gdim
    single(T.A)
    group by gdim

The aggregator single succeeds on any empty group, and returns the default value for the given data type.

See also