CREATE TABLE table_203_313 (id DECIMAL, "name" TEXT, "pennant" TEXT, "builder" TEXT, "launched" TEXT, "original name" TEXT, "fate" TEXT)

what was the next wave class oiler after wave emperor ?
SELECT "name" FROM table_203_313 WHERE "launched" > (SELECT "launched" FROM table_203_313 WHERE "name" = 'wave emperor') ORDER BY "launched" LIMIT 1
SELECT "name" FROM "table_203_313" WHERE "launched" > (SELECT "launched" FROM "table_203_313" WHERE "name" = 'wave emperor') ORDER BY "launched" NULLS FIRST LIMIT 1