Finish the rest of the practice exam

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@@ -277,3 +277,69 @@ b. Define indexes on selected attributes to speed up your query. Justify your se
 CREATE INDEX ON "Travel-Agent" (name); -- Joining on travel_agent.name
 CREATE INDEX ON Transaction (cust_name); -- filtering by cust_name
 ```
+
+## 5
+
+Suggest an appropriate recovery technique for each of the following situations.
+
+a. You were working from home and updating a database at work when the transaction was aborted.
+
+Rollback the transaction and try again.
+
+b. A customer service representative entered an incorrect data price for a customer transaction.
+Several weeks after the accounting department has processed the transaction,
+the customer returned and discovered the mistake.
+
+Add a new compensating transaction to fix the mistake.
+
+
+## 6
+
+Contrast two-tier architecture with three-tier architecture.
+
+Two tier architectures
+
+|--------|
+| Server | * storage logic
+|--------|
+| Client | * processing logic
+|        | * presentation logic
+|--------|
+
+|--------|
+| Server | * storage logic
+|        | * processing logic
+|--------|
+| Client | * presentation logic
+|--------|
+
+
+3 tier architecture
+
+|--------|
+|   db   | * storage logic
+|--------|
+|  app   | * processing logic
+|--------|
+| client | * presentation logic
+|--------|
+
+## 7
+
+a. Briefly contrast transient data with periodic data in data warehousing.
+
+> Transient data: in which changes to existing records are written over previous records, thus destroying the previous data content.
+> Periodic data: data that are never physically altered or deleted once they have been added to the store.
+
+b. Briefly discuss the characteristics of a surrogate key, as used in a data warehouse or data mart.
+
+Surrogate Key
+
+Every key used to join the fact table with a dimension table should be a surrogate (system assigned) key.
+
+Why?
+
+* Business keys change, often slowly, over time and we need to remember old and new business key values for the same business object.
+* Using a surrogate key also allows us to keep track of different non-key attribute values for the same product production key with several surrogate keys, each for the different package sizes.
+* Surrogate keys are often simpler and shorter
+* Surrogate keys can be of the same length and format for all keys