CREATE TABLE table_20928 ("Antibody" TEXT, "Brand name" TEXT, "Approval date" FLOAT, "Type" TEXT, "Target" TEXT, "Approved treatment ( s ) " TEXT)

How many targets are there with an approval date of 1997?
SELECT COUNT("Target") FROM table_20928 WHERE "Approval date" = '1997'
SELECT COUNT("Target") FROM "table_20928" WHERE "Approval date" = '1997'