Data Definition Language (DDL) and Data Manipulation Language (DML) Statements

Introduction

In the world of databases, there are two types of statements that allow us to interact with the data stored within: Data Definition Language (DDL) and Data Manipulation Language (DML) statements. These statements play a crucial role in managing and manipulating data in a database management system (DBMS). In this article, we will explore the differences between DDL and DML statements and understand how they are used.

Data Definition Language (DDL) Statements

DDL statements are responsible for defining and managing the structure or schema of a database. These statements enable us to create, modify, and delete database objects such as tables, indexes, views, and constraints. Some commonly used DDL statements include:

1. CREATE: The CREATE statement allows us to create new database objects such as tables, indexes, views, or even the database itself.
2. ALTER: The ALTER statement is used to modify the structure of existing database objects. With ALTER, we can add, modify, or delete columns, constraints, or indexes from a table, among other things.
3. DROP: The DROP statement is used to permanently remove a database object from the schema. It can be used to delete tables, indexes, views, or the entire database.
4. TRUNCATE: The TRUNCATE statement is used to delete all data from a table while preserving the table structure. It is faster than the DELETE statement for deleting all records from a table.

DDL statements are not concerned with the actual data itself but focus on defining and managing the structure of the database.

Data Manipulation Language (DML) Statements

DML statements, on the other hand, are used to manipulate the data stored within the database. They allow us to insert, retrieve, modify, and delete data from the database. Some commonly used DML statements include:

1. SELECT: The SELECT statement is used to retrieve data from one or more tables. It allows us to specify which columns to retrieve, apply filters using the WHERE clause, and perform various operations such as sorting using the ORDER BY clause.
2. INSERT: The INSERT statement is used to add new data into a table. It specifies the values to be inserted into specific columns or can retrieve data from another table.
3. UPDATE: The UPDATE statement is used to modify existing data in a table. It allows us to change the values of specific columns based on specified conditions using the WHERE clause.
4. DELETE: The DELETE statement is used to remove data from a table based on specified conditions using the WHERE clause.

DML statements are responsible for manipulating the data within the database, including retrieving, inserting, updating, and deleting records.

Conclusion

In summary, DDL and DML statements serve different purposes in managing and manipulating data within a database. DDL statements are used to define and manage the structure or schema of the database, while DML statements are used to manipulate the actual data stored within the tables.

Understanding the differences between these two types of statements is crucial for anyone working with databases. By leveraging the power of DDL and DML statements, database administrators and developers can effectively manage and manipulate data in a database management system.