CREATE TABLE table_28138035_4 (womens_singles VARCHAR2, year_location VARCHAR2)

Name the number of womens singles for 1999 rio de janeiro
SELECT COUNT(womens_singles) FROM table_28138035_4 WHERE year_location = "1999 Rio de Janeiro"
SELECT COUNT("womens_singles") FROM "table_28138035_4" WHERE "1999 Rio de Janeiro" = "year_location"