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Update README.md
TKirtan Jan 6, 2023
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81 changes: 26 additions & 55 deletions README.md
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# DBMS_SQL_Overview
# DBMS SQL Overview

## DBMS 1
--> About DBMS
- About DBMS
- ER Diagram, Entity Set, Relationship, Cardinality Constraint, Attributes, Constraints
- Keys
- Functional Dependency
- Decomposition of a Relation
- Types of Decomposition


--> ER Diagram , Entity Set , Relationship , Cardinality Constraint , Attributes , Constraints
## DBMS 2
- Normalization
- Transaction
- Acid properties
- Schedules
- Relational Algebra


--> Keys


--> Functional Dependency


--> Decomposition of a Relation


--> Types of Decomposition


##DBMS 2
--> Normalization


--> Transaction


--> Acid properties


--> Schedules


--> Relational Algebra

##DBMS 3
--> SQL


--> DDL , DML , DCL


--> SQL queries
## DBMS 3
- SQL
- DDL , DML , DCL
- SQL queries


## Deadlocks (Important):
A situation where a set of processes are blocked because each process is holding a
resource and waiting for another resource acquired by some other process. Deadlock
can arise if following four conditions hold simultaneously (Necessary Conditions):
1. Mutual Exclusion – One or more than one resource is non-sharable (Only one
process can use at a time).
2. Hold and Wait – A process is holding at least one resource and waiting for
resources.
3. No Preemption – A resource cannot be taken from a process unless the process
releases the resource.
A situation where a set of processes are blocked because each process is holding a resource and waiting for another resource acquired by some other process. Deadlock can arise if following four conditions hold simultaneously (Necessary Conditions) :

1. Mutual Exclusion – One or more than one resource is non-sharable (Only one process can use at a time).
2. Hold and Wait – A process is holding at least one resource and waiting for resources.
3. No Preemption – A resource cannot be taken from a process unless the process releases the resource.
4. Circular Wait – A set of processes are waiting for each other in circular form.

● Methods for handling deadlock: There are three ways to handle deadlock
1. Deadlock prevention or avoidance : The idea is to not let the system into a
deadlock state.
2. Deadlock detection and recovery : Let deadlock occur, then do preemption to
handle it once occurred.
3. Ignore the problem all together : If deadlock is very rare, then let it happen and
reboot the system. This is the approach that both Windows and UNIX take.
- Methods for handling deadlock: There are three ways to handle deadlock
1. Deadlock prevention or avoidance : The idea is to not let the system into a deadlock state.
2. Deadlock detection and recovery : Let deadlock occur, then do preemption to handle it once occurred.
3. Ignore the problem all together : If deadlock is very rare, then let it happen and reboot the system. This is the approach that both Windows and UNIX take.