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PREAMBLE TO RDBMS

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Databases:

Databases are computer structures that save, organize, protect and deliver data..

Types of DBMS:

  • Text Database
  • Desktop Database
  • Relational Database management system
  • Object-Oriented DataBase

Today our topic is RDBMS:

RDMS:

  • A short definition of an RDMS may be a DBMS in which data is stored in the form of tables and the relationship among the data is also stored in the form of tables.
  • E. F. Codd, the famous mathematician has introduced 12 rules for the relational model for databases commonly known as Codd’s rules.
  • The rules mainly define what is required for a DBMS for it to be considered relational, I. e.., an RDMS.

Codd’s Rules:

  • Integrity constraints
  • Logical&physical Data independence
  • High-level insert,Update,and Delete
  • Access Database using a common language (SQL)
  • Handling of null values
  • Information Rule–All data is represented in only one way(Rows& Columns)
  • Data must be accessible with no ambiguity

RDBMS softwares:

  • Oracle product of oracle corporation
  • IBM DB2 product of IBM
  • Microsoft SQL server product of Microsoft
  • Mysql product of oracle
  • Sybase product of SAP

Operating systems:

  • Red Hat Linux
  • Windows
  • Suse Linux
  • AIX

RDBMS–Client Server Architecture:

ORACLE DATABASE SERVER:

Gets file requests from clients sends files to clients receives files back from clients.

NETWORK:

  • Client A(User1): Sends SQL requests to the server, Receives files from the server, Updates data, Sends files back to the server.
  • Client B( User2): Sends SQL requests to the server, Receives files from the server, Updates data, Sends files back to Server.

http://Logical structure of RDMs

Logical Structure:

  • Data in the Database is stored in the form of rows and columns in the tables.
  • Tables are the objects created inside the datafiles
  • Databases are the collection of multiple data files.

http://Www.logical structures of RDMS

Datatypes of SQL:

SCALAR TYPES:

  • Binary integer: The binary integer datatype to store signed integers.
  • Date: Date datatype to store fixed-length datetimes
  • Long: The long data type to store variable-length character strings. The long data type is like the varchar2 datatype, except that the maximum size of the long value is 32760 bytes.
  • NChar: To store multi-byte fixed-length character data. It’s the same as char only difference is it is used to store characters of different languages like Japanese, Chinese, etc..
  • No of Characters it can be stored depend on language.

LOB:

  • Binary large object: A column or variable of type BLOB can store up to 4GB of binary data in each record.
  • Character large object: A column or variable of type CLOB can store up to 4GB of character data in each record.
  • BFILE: It can store a file of size 4GB externally outside the database for each record and can refer to that from inside the database.

IMPORTANT POINTS (LOB):

  • The column or variable of this type can be accessed only using an Oracle package DBMS_LOB.
  • This should be used only if required to store a large amount of data in each record of a table.
  • You should avoid making unnecessary use of lobs.

  • Select

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