CREATE TABLE table_204_597 (id NUMBER, "main author" CLOB, "no. of patients" NUMBER, "duration of follow-up years" NUMBER, "linearized rate of infection" CLOB, "actuarial freedom from infective endocarditis" CLOB)

how many authors have more than 500 patients ?
SELECT COUNT("main author") FROM table_204_597 WHERE "no. of patients" > 500
SELECT COUNT("main author") FROM "table_204_597" WHERE "no. of patients" > 500