CREATE TABLE table_17864 ("Constituency" TEXT, "Electorate" FLOAT, "s Spoilt vote" FLOAT, "Total poll  ( % ) " TEXT, "For  ( % ) " TEXT, "Against  ( % ) " TEXT)

List the smallest possible spoilt vote with the s r-tr ndelag constituency.
SELECT MIN("s Spoilt vote") FROM table_17864 WHERE "Constituency" = 'Sør-Trøndelag'
SELECT MIN("s Spoilt vote") FROM "table_17864" WHERE "Constituency" = 'Sør-Trøndelag'