Recent posts in Databases


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

Ashish Goyal posted in Databases Jan 28, 2019

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

dan31 posted in Databases Jan 24, 2019
by dan31

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
Join- equijoin left/right outer join, natural join- minimum and maximum number of elements
1NF- No multi-valued dependency
2NF- No partial dependency
3NF-No transitive dependency BCNF
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
Division operator
Relational Calculus- Tuple Calculus, Domain Calculus- both have same power, examples
safe and unsafe query

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
  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 AB->C ,A can be deleted if closure of B contains A
Rohan Ghosh posted in Databases Jul 28, 2015
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