Functional dependencies are the constraints that are derived from the meaning and interrelationship of the data. Let F is a set of all functional dependencies. The set of all dependencies that include F as well as all dependencies that can be inferred from F is called CLOSURE of F denoted by F+.Example 1Given below is an example of functional dependency in database management system (DBMS) −F= { SSN-> {ENMAE, BDATE, ADDRESS, DNUMBER}, DNUMBER-> {DNAME, DMGRSSN} }OutputYou will get the following result −Example 2Given below is another example of functional dependency in the DBMS −F+ = { SSN-> {ENAME, BDATE, ADDRESS, ... Read More

SQL is a Structured Query Language which is the standard and most widely used programming language for relational databases. It is used to manage and organize data in all sorts of systems where all varieties of data relationships exist.Structured Query Language (SQL) ClausesThe SQL clauses are of three types as shown below−Let us learn about them one by one.GROUP BY CLAUSESQL GROUP BY is used to arrange identical data into groups. It is used with the SQL SELECT statement. The GROUP BY statement follows the WHERE clause in a SELECT statement and precedes the ORDER BY clause. It is also ... Read More

A nested query is a query that has another query embedded within it. The embedded query is called a subquery.A subquery typically appears within the WHERE clause of a query. It can sometimes appear in the FROM clause or HAVING clause.ExampleLet’s learn about nested queries with the help of an example.Find the names of employee who have regno=103The query is as follows −select E.ename from employee E where E.eid IN (select S.eid from salary S where S.regno=103);Student tableThe student table is created as follows −create table student(id number(10), name varchar2(20), classID number(10), marks varchar2(20)); Insert into student values(1, 'pinky', 3, ... Read More

Let us understand what table, view and synonym in the structured query language (SQL) are.Table, view and synonymA table is a repository of data, where in the table it is a physical entity. A table resides physically in the database.A view is not a part of the database’s physical representation. It is precompiled, so that data retrieval behaves faster and also provides a secure accessibility mechanism.A synonym is an alternate name assigned to a table, view, sequence or program unit.ExampleCreate table employee (empID integer primary key, name varchar2(30), skill varchar2(30), salary number(20), DOB datetime).Let’s say there is a scenario where ... Read More

Delete command is a data manipulation command which is used to remove records from a table. All records may be removed in one go, or a set of records may be deleted based on a condition.Remove specific rows from tableTo remove a specific row in the table, we need to mention where condition. Based on the condition, that particular row is deleted from the table.The syntax is as follows −delete from tablename where conditionFor example, Delete from employee where name=’sneha’;ExampleGiven below is an example to remove specific rows from table −create table employee(ename varchar(30), department varchar(20), age number(30), salary number(20)); ... Read More

Update command is a data manipulation command which is used to edit the records of a table. It may be used to update a single row based on a condition, all rows or set of rows based on the condition given by the user.It is used along with the SET clause, operationally, a WHERE clause may be used to match conditions −Example 1An example is given below for the use of update command −update table student set name=’sneha’ where branch=’CSE’;Example 2Given below is another example of the usage of update command −create table employee(ename varchar(30), department varchar(20)); insert into employee ... Read More

Insert command is data manipulation commands, which is used to manipulate data by inserting the information into the tables.This command is used to add records to a table. While inserting a record using the insert statement, the number of records being entered should match in the columns of the table. In case the number of items being created is less than the number of columns, the field names also need to be specified along with the insert statement.Insert commandIt is used for inserting the records into the table.The syntax is as follows −INSERT INTO table-name VALUES(field1, field2, ……..)ExampleGiven below is ... Read More

The overall design of the Database Management System (DBMS) depends on its architecture. A large amount of data on web servers, Personal Computers (PC) and other elements are linked with networks with the help of basic client or server architecture.PCs and workstations are part of Client architecture that are connected over the network. The architecture of DBMS depends on how the users are linked to the database.There are three kinds of DBMS Architecture, which are as follows −Tier-1 Architecture.Tier-2 Architecture.Tier-3 Architecture.Tier-3 ArchitectureThe 3-tier architecture contains one more layer between the client and the server.In this architecture, there is no direct ... Read More

The overall design of the Database Management System (DBMS) depends on its architecture. A large amount of data on web servers, Personal Computers (PC) and other elements are linked with networks with the help of basic client or server architecture.PCs and workstations are part of Client architecture that are connected over the network. The architecture of DBMS depends on how the users are linked to the database.There are three kinds of DBMS Architecture, which are as follows −Tier-1 Architecture.Tier-2 Architecture.Tier-3 Architecture.Tier-2 ArchitectureThe 2-tier Architecture is based on a client-server machine.In this type of architecture, the applications on client-side interact directly ... Read More

The overall design of the Database Management System (DBMS) depends on its architecture. A large amount of data on web servers, Personal Computers (PC) and other elements are linked with networks with the help of basic client or server architecture.PCs and workstations are part of Client architecture that are connected over the network. The architecture of DBMS depends on how the users are linked to the database.There are three kinds of DBMS Architecture, which are as follows −Tier-1 Architecture.Tier-2 Architecture.Tier-3 Architecture.Tier is a physical unit where the program code or a process is run.For example − data base server, application ... Read More