A database is a collection of data or records. Database management systems are designed to work with data. A database management system (DBMS) is a software system that uses a standard method to store and organize data. The data can be added, updated, deleted, or traversed using various standard algorithms and queries.
There are several types of database management systems. Here is a list of seven common database management systems:
In a hierarchical database management systems (hierarchical DBMSs) model, data is stored in a parent-children relationship nodes. In a hierarchical database, besides actual data, records also contain information about their groups of parent/child relationships.
The data is stored in form of collection of fields where each field contains only one value. The records are linked to each other via links into a parent-children relationship. In a hierarchical database model, each child record has only one parent. A parent can have multiple children.The hierarchical database system structure was developed by IBM in early 1960s. While hierarchical structure is simple, it is inflexible due to the parent-child one-to-many relationship. Hierarchical databases are widely used to build high performance and availability applications usually in banking and telecommunications industries. The following are hierarchical databases:
Hierarchical database can be accessed and updated rapidly because in this model structure is like as a tree and the relationships between records are defined in advance. This feature is a two-edged.
This type of database structure is that each child in the tree may have only one parent, and relationships or linkages between children are not permitted, even if they make sense from a logical standpoint. Hierarchical databases are so in their design. it can adding a new field or record requires that the entire database be redefined.
Network database management systems (Network DBMSs) use a network structure to create relationship between entities. Network databases are mainly used on a large digital computers. Network databases are hierarchical databases but unlike hierarchical databases where one node can have one parent only, a network node can have relationship with multiple entities. A network database looks more like a cobweb or interconnected network of records
In network databases, children are called members and parents are called occupier. The difference between each child or member can have more than one parent.The approval of the network data model is similar to a hierarchical data model. Data in a network database is organized in many-to-many relationships. The following are network databases:
In relational database management systems (RDBMS), the relationship between data is relational and data is stored in tabular form of columns and rows. Each column if a table represents an attribute and each row in a table represents a record. Each field in a table represents a data value.
Structured Query Language (SQL) is a the language used to query a RDBMS including inserting, updating, deleting, and searching records.
Relational databases work on each table has a key field that uniquely indicates each row, and that these key fields can be used to connect one table of data to another. The following are relational databases:
In this Model we have to discuss the functionality of the object oriented Programming. It takes more than storage of programming language objects. Object DBMS's increase the semantics of the C++ and Java.I t provides full-featured database programming capability, while containing native language compatibility. It adds the database functionality to object programming languages.
The object-oriented database derivation is the integrity of object-oriented programming language systems and consistent systems. The following are object oriented databases:
The benefits to object-oriented databases are compelling. The ability to mix and match reusable objects provides incredible multimedia capability.
Object-oriented database are more expensive to develop.In the Most organizations are unwilling to abandon and convert from those databases.
An ER model is typically implemented as a database. In a simple relational database implementation, each row of a table represents one instance of an entity type, and each field in a table represents an attribute type. In a relational database a relationship between entities is implemented by storing the primary key of one entity as a pointer or "foreign key" in the table of another entity
Graph Databases are NoSQL databases and use a graph structure for sematic queries. The data is stored in form of nodes, edges, and properties. In a graph database, a Node represent an entity or instance such as customer, person, or a car. A node is equivalent to a record in a relational database system. An Edge in a graph database represents a relationship that connects nodes. Properties are additional information added to the nodes.The following are graph databases:
Graph database structure is also supported by some RDBMs including Oracle and SQL Server 2017 and later versions.
Document databases (Document DB) are also NoSQL databases that store data in form of documents. Each document represents the data, its relationship between other data elements, and attributes of data. Document database store data in a key value form.
Document DB has become popular recently due to their document storage and NoSQL properties. NoSQL data storage provide faster mechanism to store and search documents. The following are document databases:
The following are the component of database management system
A little part of data is called bit. example 0,1,null each are bit.
8 bit togather make a byte. One byte indicate a letter or a number or any symbol.
A lot of letter togather make a word or number. It is called field. Example: name or age of any man
A collection of field of mutual related is called record. Example:name,email,mobile,father name,location together is a record of a student.
A collection of record is called file. Example:record of all student is a file of student
Any person,metarials,event who can explain separately is called entity. Example:student,teacher,food
The charecter of entity is called attribute.Example:student name,role are attribute
A schema is a collection of database objects owned by a specific user. Those objects include tables, indexes, views, stored procedures, etc
In Oracle, a schema requires a user to be created. So in Oracle, the user is the account and the schema is the objects
A view is a virtual table, which provides access to a subset of column from one or more table. A view can derive its data from one or more table. An output of query can be stored as a view.
In Oracle, you can create an autonumber field by using sequences. A sequence is an object in Oracle that is used to generate a number sequence. This can be useful when you need to create a unique number to act as a primary key
A synonym is an alternative name for objects such as tables, views, sequences, stored procedures, and other database objects. You generally use synonyms when you are granting access to an object from another schema and you don't want the users to have to worry about knowing which schema owns the object.
Indexes are used in Oracle to provide quick access to rows in a table. Indexes provide faster access to data for operations that return a small portion of a table's rows. Although Oracle allows an unlimited number of indexes on a table, the indexes only help if they are used to speed up queries.
A stored procedure in PL/SQL is nothing but a series of declarative SQL statements which can be stored in the database catalogue. A procedure can be thought of as a function or a method. They can be invoked through triggers, other procedures, or applications on Java, PHP etc.
A stored function is a set of PL/SQL statements you can call by name.A function can be used as a part of SQL expression i.e. we can use them with select/update/merge commands. One most important characteristic of a function is that unlike procedures, it must return a value
A method is procedure or function that is part of the object type definition.A method is a set of code which is referred to by name and can be called (invoked) at any point in a program simply by utilizing the method's name
Oracle allows you to define procedures that are implicitly executed when an INSERT, UPDATE, or DELETE statement is issued against the associated table. These procedures are called database triggers. ... A trigger can include SQL and PL/SQL statements to execute as a unit and can invoke stored procedures.
A package is a schema object that groups logically related PL/SQL types, variables, constants, subprograms, cursors, and exceptions. A package is compiled and stored in the database, where many applications can share its contents.