What is 1994, when 1996 is "Grand Slams"?
CREATE TABLE "singles_performance_timeline" (
  "tournament" text,
  "1990" text,
  "1991" text,
  "1992" text,
  "1993" text,
  "1994" text,
  "1995" text,
  "1996" text
);
SELECT "1994" FROM "singles_performance_timeline" WHERE "1996"='grand slams';