CREATE TABLE table_203_5 (id DECIMAL, "season" TEXT, "competition" TEXT, "round" TEXT, "opponent" TEXT, "home" TEXT, "away" TEXT, "aggregate" TEXT)

does each competition have an opponent listed ?
SELECT COUNT(*) > 0 FROM table_203_5 WHERE NOT "opponent" IS NULL
SELECT COUNT(*) > 0 FROM "table_203_5" WHERE NOT "opponent" IS NULL