Understanding the Difference Between DDL and DML
When it comes to managing databases, there are two key types of commands that are essential to know: Data Definition Language (DDL) and Data Manipulation Language (DML). While both types of commands are important, they have different purposes and functionality.
What is DDL?
DDL is used to define the structure of a database, such as creating tables, defining relationships between tables, and setting up constraints. DDL commands are used to modify the structure of a database, schema, or table. These types of commands are executed less frequently than DML commands because they are typically used to set up the initial structure of a database.
Common DDL commands include:
– CREATE TABLE: This command is used to create a new table in a database.
– ALTER TABLE: This command is used to modify the structure of an existing table.
– DROP TABLE: This command is used to delete a table from a database.
– CREATE INDEX: This command is used to create indexes on columns in a table for faster searching.
What is DML?
DML is used to manage the data within a database. It includes commands that are used to insert, update, and delete data in tables. DML commands are used frequently, as they are used to manage the day-to-day operations of a database.
Common DML commands include:
– INSERT INTO: This command is used to add new rows to a table.
– UPDATE: This command is used to modify existing data in a table.
– DELETE: This command is used to remove data from a table.
Differences between DDL and DML
The key difference between DDL and DML is that DDL is used to define and modify the structure of a database, while DML is used to manage the data within a database. Another significant difference is that DDL commands are typically executed infrequently, while DML commands are executed frequently.
DDL changes are permanent and cannot be undone, while DML changes can be rolled back. This means that if you accidentally delete important data, you can use DML to restore it to a previous state.
In conclusion, understanding the difference between DDL and DML is important when it comes to managing databases. Both types of commands are essential to managing a database, but they have different purposes and are used in different ways. By knowing the difference between DDL and DML, you can better understand the structure and functionality of your databases.
Table difference between ddl and dml
| DDL (Data Definition Language) | DML (Data Manipulation Language) |
|---|---|
| DDL is used to define the structure of database objects. | DML is used to manipulate the data stored in the database objects. |
| DDL commands are used to create, alter, and delete database objects such as tables, indexes, views, and procedures. | DML commands are used to insert, update, and delete data in database tables. |
| DDL commands do not modify the data in tables. | DML commands directly modify the data in tables. |
| Some examples of DDL commands are CREATE, ALTER, DROP, and TRUNCATE. | Some examples of DML commands are INSERT, UPDATE, DELETE, and MERGE. |
| DDL commands are used to manage the structure of the database. | DML commands are used to manage the data within the database. |