CREATE TABLE table_41930 ("Week" FLOAT, "Date" CLOB, "Opponent" CLOB, "Result" CLOB, "Attendance" CLOB)

On what date did the Bills play the Houston Oilers before week 12?
SELECT "Date" FROM table_41930 WHERE "Week" < '12' AND "Opponent" = 'houston oilers'
SELECT "Date" FROM "table_41930" WHERE "Opponent" = 'houston oilers' AND "Week" < '12'