SQL Queries

Question :

SQL Queries for Book Library Database Design.

Answer :

SQL Queries

Almost all relational database management systems use SQL (Structured Query Language) for data manipulation and retrieval. SQL is the standard language for relational database systems. SQL is a non-procedural language.

DDL(Data Definition Language) Queries

DDL commands are used to define the data. For example, CREATE TABLE.

The CREATE TABLE Statement:

The CREATE TABLE statement is used to create a table in a database.

Now we want to create a table called "Student" that contains three columns: StudentId,StudentFirstName,StudentLastName.

create table Student_tbl(StudentId  int primary key,

StudentFirstName  varchar(50) ,

StudentLastName  varchar(50) 

);

Table Created;

Drop Statement:

Indexes, tables, and databases can easily be deleted/removed with the DROP statement.

DROP TABLE Cources;

Alter Statement:

The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

SQL ALTER TABLE Syntax:

ALTER TABLE Student
ADD DateOfBirth date

DML(Data Manilpulation Language) Queries

DML commands such as, INSERT and DELETE are used to manipulate data.

The SELECT Statement:

The SELECT statement is used to select data from a database. If we select particular Column from the “Student” Table than SQL Queries is,

SELECT StudentFirstName
FROM Student;

If we want to select all the columns from the "Student" table than SQL Queries is.

SELECT * FROM Student;

The INSERT INTO Statement:

The INSERT INTO statement is used to insert a new row in a table.

SQL INSERT INTO Syntax: It is possible to write the INSERT INTO statement in two forms. The first form doesn't specify the column names where the data will be inserted, only their values:

INSERT INTO table_name
VALUES (value1, value2, value3,...)

The second form specifies both the column names and the values to be inserted:

INSERT INTO table_name (column1, column2, column3,...)
VALUES (value1, value2, value3,...)

Now we want to insert a new row in the "Student" table.

INSERT INTO Student_tbl ( StudentId,   StudentFirstname, StudentLastName )

VALUES (5, 'Lakshmi', 'Gupta');

Table Created;

The Delete Statement:

The DELETE statement is used to delete rows in a table.

SQL DELETE Syntax:

DELETE FROM table_name
WHERE some_column=some_value

Now we want to delete the person "Denny, Jain" in the "Student" table.

Delete All Rows: It is possible to delete all rows in a table without deleting the table. This means that the table structure, attributes, and indexes will be intact:

DELETE FROM table_name

or

DELETE * FROM table_name

SQL Queries

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