SELECT * FROM Student WHERE Age <= 18 ORDER BY Name;
 

(i) The DISTINCT keyword is used along with the SELECT command to eliminate duplicate rows in the table. This helps to eliminate redundant data.

(ii) For Example: SELECT DISTINCT Place FROM Student;
    Will display the following data as follows:
    Place
    Chennai
    Banglore
    Delhi

 

(i) The SAVEPOINT command is used to temporarily save a transaction so that you can rollback to the point whenever required.
(ii) The different states of our table can be saved at any time using different names and the rollback to that state can be done using the ROLLBACK command.
(iii) SAVEPOINT savepoint_name:
      UPDATE student SET Name = 'Mini' WHERE Admno=105;
      SAVEPOINT A;

Data Definition Language:
(i) Create Command: To create tables in the database.
CREATE TABLE Student
(Admno integer,
      Name char(20),
      Gender char(1),
      Age integer,
      Place char(10),
);
(ii) Alter Command: The ALTER command is used to alter the table structure like adding a column, renaming the existing column, change the data type of any column or size of the column or delete the column from the table.
ALTER TABLE <table-name> ADD <column-name><data type><size>;
To add a new column "Address" of type 'char' to the Student table, the command is used as
ALTER TABLE Student ADD Address char;
(iii) Drop Command: The DROP TABLE command is used to remove a table from the database.
The table can be deleted by DROP TABLE command in the following way:
DROP TABLE table-name;

1. SELECT * FROM student WHERE gender = Male GROUP BY gender;
2. SELECT * FROM student WHERE Age > 18 ORDER BY DESC;

SQL commands are divided into five categories:

Data Definition Language:
(i) The Data Definition Language (DDL) consist of SQL statements used to define the database structure or schema.
(ii) It simply deals with descriptions of the database schema and is used to create and modify the structure of database objects in databases.
(iii) The DDL provides a set of definitions to specify the storage structure and access methods used by the database system.
DDL performs the following functions:
(i) It should identify the type of data division such as data item, segment, record and database file.
(ii) It gives a unique name to each data item type, record type, file type and data base.
(iii) It should specify the proper data type.
(iv) It should define the size of the data item.
(v) It may define the range of values that a data item may use.
(vi) It may specify privacy locks for preventing unauthorized data entry.
Commands:

Data Manipulation Language:
This is a computer programming language used for adding, removing and modifying data in a database. This language comprises the SQL-data change statements, which modify stored data but not the schema of the database table
Data Manipulation includes
(i) Insertion of new information into the database
(ii) Retrieval of information stored in a database
(iii) Deletion of information from the database.
(iv) Modification of data stored in the database
The DML is basically of two types:
Procedural DML - Requires a user to specify what data is needed and how to get it.
Non-Procedural DML - Requires a user to specify what data is needed without Specifying how to get it.
Commands:

Data Control Language:
(i) A Data Control Language (DCL) is a programming language used to control the access of data stored in a database. It is used for controlling privileges in the database (Authorization).
(ii) The privileges are required for performing all the database operations such as creating sequences, views of tables etc.
Commands:

Transactional Control Language:
Transactional control language (TCL) commands are used to manage transactions in the database. These are used to manage the changes made to the data in a table by DML statements.
Commands:

Data query language:
The Data Query Language consist of commands used to query or retrieve data from a database. One such SQL command in Data Query Language is