Introduction to DBMS

• The raw facts constitutes data
• Information is the processed or organized form of data.
• A database is a collection of logically related data items stored in an organised manner.
• The software that is used to create, update and retrieve data is known as database management system (DBMS). I
• A database can be designed in different ways depending on the data being stored. This structure of database is known as data model that describes the manner in which data will be stored and retrieved.
• Hierarchical Data Model:

  In this model the data is organized into a tree like structure.The data is stored in the form of records.
• The data is stored in the form of records.
• A record is a collection of fields and its data values.
• Network model:

  multiple records are linked to same master file. It is also considered as an inverted tree where master is present in the bottom of the tree and the branches contain information linked to the master.
• Relational data model:

  This data model is based on the principle of setting relationships between two or more tables of the same database. It is the most commonly used database model.
• entity is a real world object about which information is to be stored in a database.
• The details associated with the entity are called attributes.
• A table is a collection of logically related records.
• A table is a collection of logically related records.
• A primary key or simply a key is a field that uniquely identifies a row in a table.
• If, in a table we use more than one fields to identify a record, it is known as a composite key
• A relational database is a collection of related tables.
• If a field or a combination of fields of one table can be used to uniquely identify records of another table, then that particular field is known as the foreign key
• All the field values that are eligible to be the primary key are the candidate keys for that table.
• Out of the candidate keys, one or two are made as primary keys. The others are the alternate keys.
• An object in a database is a structure or a feature that is used to store, represent or retrieve data.
• A form is a feature of a database using which we can enter data in a table in an easy and user friendly manner.
• A query is used to retrieve the desired information from the database.
• A query is used to retrieve the desired information from the database.