CREATE TABLE table_204_77 (id NUMBER, "number" CLOB, "builder" CLOB, "type" CLOB, "date" CLOB, "works number" NUMBER, "notes" CLOB)

how many different types of diesel locomotives are dated after 1980 ?
SELECT COUNT("number") FROM table_204_77 WHERE "date" > 1980
SELECT COUNT("number") FROM "table_204_77" WHERE "date" > 1980