CREATE TABLE table_203_645 (id DECIMAL, "lower mississippi periods" TEXT, "lower yazoo phases" TEXT, "lower yazoo\ dates" TEXT, "tensas/natchez phases" TEXT, "cahokia phases" TEXT, "cahokia dates" TEXT, "ohio/miss. river\ confluence phases" TEXT, "ohio/miss. dates" TEXT)

how many lower yazoo phases are there ?
SELECT COUNT(DISTINCT "lower yazoo phases") FROM table_203_645
SELECT COUNT(DISTINCT "lower yazoo phases") FROM "table_203_645"