CREATE TABLE table_15677 ("Artist" TEXT, "Country of origin" TEXT, "Period active" TEXT, "Release-year of first charted record" FLOAT, "Genre" TEXT, "Claimed sales" TEXT)

What was the earliest release-year of the first charted record of Abba?
SELECT MIN("Release-year of first charted record") FROM table_15677 WHERE "Artist" = 'abba'
SELECT MIN("Release-year of first charted record") FROM "table_15677" WHERE "Artist" = 'abba'