Which of the following are DDL commands

Data Definition Language helps you to define the database structure or schema. DDL commands help you to create the structure of the database and the other database objects. Its commands are auto-committed so, the changes are saved in the database permanently. The full form of DDL is Data Definition Language.

What is DML?

DML commands it to allow you to manage the data stored in the database, although DML commands are not auto-committed. Moreover, they are not permanent. So, It is possible to roll back the operation. The full form of DML is Data Manipulation Language.

Difference Between DDL and DML in DBMS

Here is the main difference between DDL and DML Command in DBMS:

Why DDL?

Here, are reasons for using DDL method:

• Allows you to store shared data
• Data independence improved integrity
• Allows multiple users
• Improved security efficient data access

Why DML?

Here, benefits/ pros of DML:

• The DML statements allow you to modify the data stored in a database.
• Users can specify what data is needed.
• DML offers many different flavors and capabilities between database vendors.
• It offers an efficient human interaction with the system.

Commands for DDL

Five types of DDL commands are:

CREATE

CREATE statements is used to define the database structure schema:

Syntax:

CREATE TABLE TABLE_NAME (COLUMN_NAME DATATYPES[,....]); 

For example:

Create database university;
Create table students;
Create view for_students;

DROP

Drops commands remove tables and databases from RDBMS.

Syntax:

DROP TABLE ;  

For example:

Drop object_type object_name;
Drop database university;
Drop table student;

ALTER

Alters command allows you to alter the structure of the database.

Syntax:

To add a new column in the table

ALTER TABLE table_name ADD column_name COLUMN-definition;  

To modify an existing column in the table:

ALTER TABLE MODIFY(COLUMN DEFINITION....); 

For example:

Alter table guru99 add subject varchar;

TRUNCATE:

This command used to delete all the rows from the table and free the space containing the table.

Syntax:

TRUNCATE TABLE table_name;  

Example:

TRUNCATE table students;

Commands for DML

Here are some important DML commands:

• INSERT
• UPDATE
• DELETE

INSERT:

This is a statement that is a SQL query. This command is used to insert data into the row of a table.

Syntax:

INSERT INTO TABLE_NAME  (col1, col2, col3,.... col N)  
VALUES (value1, value2, value3, .... valueN);  
Or 
INSERT INTO TABLE_NAME    
VALUES (value1, value2, value3, .... valueN);    

For example:

Create database university;
Create table students;
Create view for_students;

UPDATE:

This command is used to update or modify the value of a column in the table.

Syntax:

Create database university;
Create table students;
Create view for_students;

For example:

Create database university;
Create table students;
Create view for_students;

DELETE:

This command is used to remove one or more rows from a table.

Syntax:

Create database university;
Create table students;
Create view for_students;

For example:

Create database university;
Create table students;
Create view for_students;

DDL Command Example

CREATE

Syntax:

Create database university;
Create table students;
Create view for_students;

Here,

• The parameter tableName denotes the name of the table that you are going to create.
• The parameters column_1, column_2… denote the columns to be added to the table.
• A column should be specified as either NULL or NOT NULL. If you don’t specify, SQL Server will take NULL as the default

Example:

Create database university;
Create table students;
Create view for_students;

ALTER

Syntax:

Create database university;
Create table students;
Create view for_students;

Example:

Create database university;
Create table students;
Create view for_students;

DROP

Syntax:

Create database university;
Create table students;
Create view for_students;

The parameter tableName is the name of the table that is to be deleted.

Example:

DROP TABLE ;  

DML Command Example

INSERT

In PL/SQL, we can insert the data into any table using the SQL command INSERT INTO. This command will take the table name, table column, and column values as the input and insert the value in the base table.

The INSERT command can also take the values directly from another table using ‘SELECT’ statement rather than giving the values for each column. Through ‘SELECT’ statement, we can insert as many rows as the base table contains.

Syntax:

DROP TABLE ;  

The above syntax shows the INSERT INTO command that takes the values directly from the using the SELECT command.

What is the DDL command?

What is DDL command with example?

Which of the following are DDL commands Mcq?

How many DDL commands are there?