CREATE TABLE table_204_520 (id NUMBER, "outcome" CLOB, "no." NUMBER, "date" NUMBER, "championship" CLOB, "surface" CLOB, "opponent" CLOB, "score" CLOB)

what surface was used before carpet ?
SELECT "surface" FROM table_204_520 WHERE id = (SELECT id FROM table_204_520 WHERE "surface" = 'carpet') - 1
SELECT "surface" FROM "table_204_520" WHERE "id" = (SELECT "id" FROM "table_204_520" WHERE "surface" = 'carpet') - 1