CS 405G: Introduction to Database Systems 26 Final exam review Chen Qian University of Kentucky

Chen Qian @ University of Kentucky Final exam Tuesday 05/05/14 10:30 – 12:00 This classroom. 4/25/2017 Chen Qian @ University of Kentucky

Read the mid-term review ER diagram Relational Algebra SQL (important!) 4/25/2017 Chen Qian @ Univ of Kentucky

Functional dependencies A functional dependency (FD) has the form X -> Y, where X and Y are sets of attributes in a relation R X -> Y means that whenever two tuples in R agree on all the attributes in X, they must also agree on all attributes in Y 4/25/2017 Chen Qian @ Univ of Kentucky

Chen Qian @ University of Kentucky FD examples Address (street_address, city, state, zip) street_address, city, state -> zip zip -> city, state zip, state -> zip? This is a trivial FD Trivial FD: LHS RHS zip -> state, zip? This is non-trivial, but not completely non-trivial Completely non-trivial FD: LHS ∩ RHS = ? 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ Univ of Kentucky Attribute closure Given R, a set of FD’s F that hold in R, and a set of attributes Z in R: The closure of Z (denoted Z+) with respect to F is the set of all attributes {A1, A2, …} functionally determined by Z (that is, Z -> A1 A2 …) Algorithm for computing the closure Start with closure = Z If X -> Y is in F and X is already in the closure, then also add Y to the closure Repeat until no more attributes can be added 4/25/2017 Chen Qian @ Univ of Kentucky

Using attribute closure Given a relation R and set of FD’s F Does another FD X -> Y follow from F? Compute X+ with respect to F If Y X+, then X -> Y follow from F Is K a super key of R? Compute K+ with respect to F If K+ contains all the attributes of R, K is a super key Is a super key K a key of R? Test where K’ = K – { a | a K} is a superkey of R for all possible a 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky Rules of FD’s Armstrong’s axioms Reflexivity: If Y X, then X -> Y Augmentation: If X -> Y, then (X,Z) -> (Y,Z) for any Z Transitivity: If X -> Y and Y -> Z, then X -> Z Rules derived from axioms Splitting: If X -> YZ, then X -> Y and X -> Z Combining: If X -> Y and X -> Z, then X -> YZ 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky First Normal Form ( 1NF ) A relation is in first normal form if the domain of each attribute contains only atomic values, and the value of each attribute contains only a single value from that domain. 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky 2nd Normal Form An attribute A of a relation R is a nonprimary attribute if it is not part of any key in R, otherwise, A is a primary attribute. R is in (general) 2nd normal form if every nonprimary attribute A in R is not partially functionally dependent on any key of R How to identify 2NF How to decompose relations 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky Third normal form 3NF requires that there are no non-trivial functional dependencies of non-key attributes on something other than a superset of a candidate key. Recall: non-trivial FD means LHS has no intersection with RHS. In summary, all non-key attributes are mutually independent. 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky BC normal form A table is said to be in the BCNF if and only if it is in the 3NF and every non-trivial, left-irreducible functional dependency has a candidate key as its determinant. How to find violations How to decompose relations 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky Conflicts precedence graph conflict-serializable schedule 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky Lock exclusive lock and shared locks Two-phase locking All lock requests precede all unlock requests Strict 2PL Only release locks at commit/abort time Examples 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky Disk Disk structure Cylinder, platter, track, etc. Random disk access Seek time + rotational delay + transfer time 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky File Storage Heap file as a list or page directory Record format Page layout 4/25/2017 Chen Qian @ University of Kentucky

Tree-Structured Indexes: Introduction Tree-structured indexing techniques support both range selections and equality selections. ISAM =Indexed Sequential Access Method static structure; early index technology. B+ tree: dynamic, adjusts gracefully under inserts and deletes. Operations: search, range query, insert, delete (important!) Understand the examples in the exercise slides! 4/25/2017 Chen Qian @ University of Kentucky 2

Chen Qian @ University of Kentucky Hashing Static hashing Dynamic hashing Extensible and linear hashing Understand examples in slides 4/25/2017 Chen Qian @ University of Kentucky 3

Chen Qian @ University of Kentucky Final Exam 1. True/False 2. Functional Dependency and Normal Forms 3. SQL 4. Index (B+ Tree) 5. Index (B+ Tree) 6. Storage 4/25/2017 Chen Qian @ University of Kentucky

Chen Qian @ University of Kentucky Good luck and hope you enjoy this class! Don’t forget: You give me a grade 4/25/2017 Chen Qian @ University of Kentucky