changed 'amount' column to two credit/debit columns

dnd_bank.psql

@@ -13,7 +13,8 @@ CREATE TABLE balance (
 CREATE TABLE transaction (
     id SERIAL PRIMARY KEY,
     account INT NOT NULL,
-    amount NUMERIC(16,2) NOT NULL,
+    withdrawal NUMERIC(16,2),
+    deposit NUMERIC(16,2),
     timestamp TIMESTAMP NOT NULL,
     FOREIGN KEY (account) REFERENCES account (id)
 );