1 Final Review Tuesday, March 6, 2007

2 The Final Date: Tuesday, March 13, 2007 Time: 6:30 - 8:30 Room: EE 037 You must come to campus Open book exam :) No computers :(

3 Problem 1: Queries SQL XPath/XQuery

4 SQL Select-from-where Subqueries Aggregation Nulls Outer joins Database modifications (insert/delete) A tricky query: for each product, find total sales in November

5 XPath/XQuery Xpath: simple navigation /, //, *, […] Xquery: nest/unnest/renest/aggregates A tricky query: eliminate duplicates in a collection of elements

6 Problem 2: Data Modeling E/R diagrams Functional dependencies and normal forms XML and semistructured data

7 E/R Diagrams Relationships Inheritance Weak entity sets Mapping to relations SQL DDL: –Creating tables –Constraints A tricky question: map a complex inheritance graph to relations

8 Functional Dependencies Basic definitions Computing the closure X+ Computing the keys Checking if a relation is in BCNF Decomposing into BCNF Tricky questions: find FD’s in a view; give counterexamples to FDs

9 XML XML syntax DTD From relations to XML From XML to relations A tricky question: N/A

10 Problem 3: Transactions Recovery Concurrency control

11 Recovery Undo log Redo log Undo/redo log A tricky question: place a missing END-CHECKPOINT

12 Concurrency control Serializability and conflict serializability Locks Timestamps Validation A tricky question: tell what happens in a schedule

13 Problem 4: Query Processing Engine Storage of database elements Indexes Logical algebra Physical algebra Optimizations Size/cost estimation

14 Storage of Database Elements Storing records in blocks Storing attributes in records A tricky question: N/A

15 Index Structures Types of indexes: –Dense/sparse index –Primary/secondary index B + -trees Hash tables: –Extensible hash tables A tricky question: perform insert/delete in a B+ tree or hash table

16 Logical Algebra Operators –Some interesting ones: natural joins, semijoins Converting SQL into the algebra A tricky question: SQL with NOT EXISTS to RA

17 Physical Operators One-pass algorithms Nested-loop joins Two-pass algorithms based on sorting Two-pass algorithms based on hash tables Index-based algorithms Their cost A tricky question: N/A

18 Optimizations Algebraic laws The dynamic programming algorithm Pipelining A tricky question: discuss alternative plans for a query

19 Size/Cost Estimation Simple size estimation formulas for selection and join Histograms –Eqdepth, eqwidth A tricky question: N/A

20 General Advice Some problems will require thinking –Use judgment Problem difficulty may be uneven: –do the easy ones first

21 Grading –Homework 35% –Project: 35% –Final: 30%

22 COMMIT (The End)