Task: Text to Code
Input (English): Step 1: For each row in bank table, find corresponding rows in customer table and in loan table.
Step 2: find the average credit_score in the results of step 1 whose loan_type equals Mortgages
Output (English): SELECT Avg ( T2.credit_score ) FROM bank AS T1 JOIN customer AS T2 ON T2.branch_ID = T1.branch_ID JOIN loan AS T3 ON T1.branch_ID = T3.branch_ID WHERE T3.loan_type = "Mortgages"