DBMS Unit-1 Part-2 Introduction

Que1.9. What are data models? Compactly explain different types of data models. Answer Data models 1. Data models define how the logical structure of the database is modeled. 2. Data models are a collection of abstract tools for describing data, data connections, data semantics and thickness constraints. 3. Data models define how data is connected to each other and how they are reused and stored inside the system. Types of data models 1. reality relationship model a. The reality relationship( ER) model consists of a collection of introductory objects, called realities and of connections among these realities. realities are represented by means of their parcels, called attributes. Attribute Attribute Attribute Attribute reality Relationship reality 1.9.1. The ER model. 2. Relational model a. The relational model represents data and connections among data by a collection of tables, each of which has a number of columns with unique names. Relational data model is used for data storehouse and processing. c. This model is simple and it has all the parcels and capabilities needed to reuse data with storehouse effectiveness. 3. Hierarchical model a. In hierarchical model data rudiments are linked as an reversed tree structure( root at the top with branches formed below). Below the single root data element are inferior rudiments each of which in turn has its own inferior rudiments and so on, the tree can grow to multiple situations. Data element has parent child relationship as in a tree. 4. Network model a. This model is the extension of hierarchical data model. b. In this model there live a parent child relationship but a child data element can have further than one parent element or no parent at all. 5. Object- acquainted model Object- acquainted models were introduced to overcome the failings of conventional models like relational, hierarchical and network model. b. An object- acquainted database is collection of objects whose geste
, state, and connections are defined in agreement with objectoriented generalities( similar as objects, class,etc.). Que1.10. Describe data schema and cases. Answer 1. The description of a database is called the database schema, which specified during database design and isn’t anticipated to change constantly. 2. utmost of the data models have certain convention for displaying schema as illustration which is called as schema illustration. 3. A schema illustration displays only some aspects of a schema, similar as the names of record types and data particulars, and some types of constraints. For illustration Schema illustration for studentinfo database Pupil( Name,Student_number, Class, Branch) Course(Course_name,Course_number, Department) Cases 1. The data in the database at a particular moment is called a database state or shot. It’s also called the current set of circumstances or cases in the database. 2. In a database state, each schema construct has its own current set of cases. 3. numerous database countries can be constructed to correspond to a particular database schema. Every time we fit or cancel a record or change the value of a data item in a record, we change one state of the database into another state. Que1.11. Describe data independence with its types. OR Explain data independence with its types. Answer Data independence Data independence is defined as the capacity to change the schema at one position of a database system without having to change the schema at the coming advanced position. Types of data independence 1. Physical data independence Physical data independence is the capability to modify internal schema without changing the abstract schema. revision at the physical position is sometimes necessary in order to ameliorate performance. c. It refers to the impunity of the abstract schema to change in the internal schema. exemplifications of physical data independence are reorganizations of lines, adding a new access path or modifying indicators,etc. 2. Logical data independence Logical data independence is the capability to modify the abstract schema without having to change the external schemas or operation programs. b. It refers to the impunity of the external model to changes in the abstract model. exemplifications of logical data independence are addition/ junking of realities. Que1.12. Describe the bracket of database language. Which type of language is SQL? OR bandy the following terms( i) DDL Command( ii) DML command. Answer Bracket of database languages 1. Data Definition Language( DDL) DDL is set of SQL commands used to produce, modify and cancel database structures but not data. They’re used by the DBA to a limited extent, a database developer, or operation inventor. produce, drop, alter, elide are generally used DDL command. 2. Data Manipulation Language( DML) a. A DML is a language that enables druggies to pierce or manipulates data as organized by the applicable data model. b. There are two types of DMLs Procedural DMLs It requires a stoner to specify what data are demanded and how to get those data. ii. Declarative DMLs(Non-procedural DMLs) It requires a stoner to specify what data are demanded without specifying how to get those data. fit, modernize, cancel, query are generally used DML commands. 3. Data Control Language( DCL) It’s the element of SQL statement that control access to data and to the database. Commit, rollback command are used in DCL. 4. Data Query Language( DQL) It’s the element of SQL statement that allows getting data from the database and assessing ordering upon it. b. It includes select statement. 5. View Definition Language( VDL) 1. VDL is used to specify stoner views and their mapping to abstract schema. 2. It defines the subset of records available to classes of druggies. 3. It creates virtual tables and the view appears to druggies like abstract position. 4. It specifies stoner interfaces. SQL is a DML language. Que1.13. Explain all database languages in detail with illustration. Answer DDL produce, ALTER, DROP, TRUNCATE, COMMENT, GRANT, drop statement DML INSERT, UPDATE, cancel statement DCL entitlement and drop statement DQL SELECT statement VDL 1. produce view emp5 as select * from hand where dno = 5; Creates view for dept 5 workers. 2. produce view empdept as select fname, lname, dno, dname from hand, department where dno = dnumber; Creates view using two tables. Que1.14. Explain DBMS interfaces. What are the colorful DBMS interfaces? Answer DBMS interfaces A database operation system( DBMS) interface is a stoner interface which allows for the capability to input queries to a database without using the query language itself. colorful DBMS interfaces are 1. Menu- grounded interfaces for web guests or browsing a. These interfaces present the stoner with lists of options( called menus) that lead the stoner through the expression of a request. Pull- down menus are a veritably popular fashion in Web- grounded stoner interfaces. They’re also frequently used in browsing interfaces, which allow a stoner to look through the contents of a database in an exploratory and unshaped manner. 2. Forms- grounded interfaces a. A forms- grounded interface displays a form to each stoner. druggies can fill out all of the form entries to fit new data, or they can fill out only certain entries, in which the DBMS will recoup matching data for the remaining entries. 3. Graphical stoner interfaces( GUI) a. A GUI generally displays a schema to the stoner in diagrammatic form. b. The stoner also can specify a query by manipulating the illustration. In numerous cases, GUIs use both menus and forms. 4. Natural language interfaces a. A natural language interface has its own schema, which is analogous to the database abstract schema, as well as a wordbook of important words. b. The natural language interface refers to the words in its schema, as well as to the set of standard words in its wordbook to interpret the request. , the interface generates a highlevel If the interpretation is successful. query corresponding to the natural language request and submits it to the DBMS for processing; else, a dialogue is started with the stoner to clarify the request. 5. Speech input and affair a. The speech input is detected using a library of predefined words and used to set up the parameters that are supplied to the queries. b. For affair, a analogous conversion from textbook or figures into speech takes place. 6. Interfaces for the DBA a. utmost database systems contain privileged commands that can be used only by the DBA’s staff. b. These include commands for creating accounts, setting system parameters, granting account authorization, changing a schema, and reorganizing the storehouse structures of a database.

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