Recent posts in Databases

Recent posts in Databases
1

Found this note quite useful in clearing my doubts with NULL. Hope this may help you!

http://www-cs-students.stanford.edu/~wlam/compsci/sqlnulls

Ashish Goyal posted in Databases Jan 28, 2019
by Ashish Goyal
4 8 13
569 views
2

Here is a concise note on Indexing, B & B+ Tree

http://www.cs.montana.edu/~halla/csci440/n18/n18.html

dan31 posted in Databases Jan 24, 2019
by dan31
9 20 30
673 views
3

For this course we will be using the LAB exercises given here which are from Silberschatz book. 
Solutions to Practice Exercises of Silberschatz book.
 

 
Day Date Contents Slides Assignments
1 Oct 7 Introduction to Databases- topics to be covered    
2 Oct 8 Relational Databases
Tuple, Domain, Attribute
Keys- candidate key, primary key, super key, foreign key
Relational algebra, SQL, Relational calculus- same power
Examples
Join- equijoin left/right outer join, natural join- minimum and maximum number of elements
Normalisation
1NF- No multi-valued dependency
2NF- No partial dependency
3NF-No transitive dependency BCNF
BCNF, 4NF
Is normalisation good?- additional join operations, expensive, it is good theoretically
Given a relation, can we make BCNF?
Is there an algorithm for this?
It is possible- but we lose something!
Normalization Notes Assignment 1
3 Oct 9 Relational Algebra
Join- theta join, equi join, natural join, semi join, outer join
Examples
Division operator
Relational Calculus- Tuple Calculus, Domain Calculus- both have same power, examples
safe and unsafe query

 
Assignment-2
Assignment-3
4 Oct 10 Normalisation revisited- Functional dependency    
5 Nov 5 Indexing
index- <key, block address>
primary index, clustered index, secondary index
How many clustered index a table can have?- atmost one clusteed index
Sparse index and dense index
primary-dense/ sparse ,clustering- sparse/ dense, secondary-dense
   
6 Nov 7 B tree and B+ tree
B tree- record pointer present in all nodes whereas in B+ tree record pointer present 
in leaf nodes only
Indexing- order of leaf and non-leaf node
B+ tree more advantage (no unnecessary block access- in B tree record 
pointer present in internal nodes)
Insertion and deletion algorithm
Entity Relationship Model- entity, attributes
Conversion of ER diagram to relational tables- 1:1, m:1, m:n, weak entity
total and partial participation
minimal normalisation satisfied- 2NF because a table formed from an entity with composite key may have a partial dependency
   

 

Manoja Rajalakshmi A posted in Databases Nov 7, 2018
by Manoja Rajalakshmi A
11 30 78
598 views
5
  1. Split the fd's such that rhs contains single attribute. 
  2. Find the redundant fd's and remove redundant ones. 
  3. Find the redundant attributes on lhs and remove them.like AB->C ,A can be deleted if closure of B contains A
Rohan Ghosh posted in Databases Jul 28, 2015
by Rohan Ghosh
3 12 26
732 views
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