Task: Text to Code
Input (English): Step 1: For each row in Campuses table, find corresponding rows in csu_fees table and in enrollments table.
Step 2: find the average CampusFee in the results of step 1 whose csu_fees's Year equals 2005 and enrollments's Year equals 1956
Output (English): SELECT Avg ( T2.CampusFee ) FROM Campuses AS T1 JOIN csu_fees AS T2 ON T2.Campus = T1.Id JOIN enrollments AS T3 ON T1.Id = T3.Campus WHERE T2.Year = 2005 AND T3.Year = 1956