DDL refers to a computer language that is primarily used for creating as well as modifying the structure of the database objects present in a database. Such database objects include indexes, tables, schemas, views, and many more. DQL statements are used for performing queries on the data within schema objects. The purpose of the DQL Command is to get some schema relation based on the query passed to it. We can define DQL as follows it is a component of SQL statement that allows getting data from the database and imposing order upon it. This command allows getting the data out of the database to perform operations with it.

In the following, we will demonstrate SQL syntax commands supporting Microsoft Access and run one command at a time. SQL stands for “Structured Query Language,” which implies (erroneously) that the language can be used only for querying. Of course, it CAN be used for querying – but it can also be used to create database components. This table example adds the constraint of a primary key that’s unique (no repeating values are allowed) to the Artist table. Remember that primary keys will always enforce a unique value. Data definition language may sound like it’s another programming language, but it’s actually a method of categorizing the different types of SQL commands.

Concurrency Control

The main DDL commands are create, alter, drop and truncate. These commands are used to update the database schema that’s why they come under basis sql. In this article, we will discuss the overview of DDL commands and will understand DDL commands like create, alter, truncate, drop. We will cover each command syntax with the help of an example for better understanding.

DDL is used for defining structure of the table such as create a table or adding a column to table and even drop and truncate table. As the name suggest DML used for manipulating the data of table. There are some commands in DML such as insert and delete.

Data modeling

It is used to retrieve, store, modify, delete, insert and update data in database. A drop command is used to delete objects such as a table, index or view. A DROP statement cannot be rolled back, so once an object is destroyed, there’s no way to recover it.

To store data in a well-structured manner, the first step with SQL is to establish a database. To build a new database in SQL, use the CREATE DATABASE statement. In some database environments, we can run more than one command at a time. The commands would be located in a file and would be submitted as a batch to be executed. DML (Data Manipulation Language) commands need to be commited/rolled back.