CREATE TABLE table_51942 ("Name" TEXT, "Street address" TEXT, "Years as tallest" TEXT, "Height ft  ( m ) " TEXT, "Floors" FLOAT)

How many floors does the building on 800 Boylston Street have?
SELECT MAX("Floors") FROM table_51942 WHERE "Street address" = '800 boylston street'
SELECT MAX("Floors") FROM "table_51942" WHERE "Street address" = '800 boylston street'