CREATE TABLE table_18648 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

How many districts does riley joseph wilson?
SELECT COUNT("District") FROM table_18648 WHERE "Incumbent" = 'Riley Joseph Wilson'
SELECT COUNT("District") FROM "table_18648" WHERE "Incumbent" = 'Riley Joseph Wilson'