Difference between DDL and DML in DBMS

Anybody dealing with databases must comprehend the distinction between DDL and DML commands because it has an impact on how data is saved, accessed, and modified.

• A collection of commands called DDL are used to specify a database's structure. Database objects including tables, views, indexes, and constraints can be created, modified, and deleted using these commands. DDL statements specify how the data is arranged and accessed rather than altering the data that is stored in the database.

• DML, on the other hand, is a set of instructions used to work with the data that is kept in the database. Data from the database can be inserted, updated, deleted, and retrieved using these procedures. DML statements alter the data that is stored in the database, not the database's structure.

What are DDL Commands?

A series of commands called DDL (Data Definition Language) is used to specify a database's structure. Database objects including tables, views, indexes, and constraints are created, modified, and deleted using DDL statements. These statements specify how the data is arranged and accessed rather than manipulating the data that is kept in the database.

DDL statements, as examples, include:

• CREATE TABLE − Used to create a new table in the database.

• ALTER TABLE − Used to modify the structure of an existing table in the database.

• DROP TABLE − Used to delete a table and all its data from the database.

• CREATE INDEX − Used to create an index on one or more columns in a table.

• CREATE VIEW − Used to create a virtual table based on the result of a query.

During the design and upkeep of a database, DDL statements are often executed by database administrators or developers. These declarations are necessary to guarantee that the database structure is clear and well-suited for effective data storage and retrieval.

Uses of DDL Commands

Following are the uses of DDL commands:

• Table creation − To add new tables to a database, use DDL commands like CREATE TABLE. The columns and data types of the data that will be stored in the database are specified by tables.

• Table modification − To change the structure of an existing table, use DDL statements like ALTER TABLE. For instance, you can alter the data type of a column, add a constraint, or add additional columns to a table.

• Table deletion − To remove tables from a database, use DDL commands like DROP TABLE. Moreover, this operation clears off all of the table's data.

• Making indexes − To make indexes on one or more table columns, use DDL statements like CREATE INDEX. The performance of queries that look for specific values in the indexed columns is enhanced by indexes.

• View creation − Virtual tables are created depending on the results of queries using DDL commands like CREATE VIEW. Views are helpful for limiting access to particular columns or rows of data and simplifying complex queries.

What are DML Commands?

A collection of instructions known as DML (Data Manipulation Language) is used to alter database-stored data. Data from tables in a database can be inserted, updated, deleted, and retrieved using DML statements. These statements alter the data that is stored in the database, not the database's structure.

DML statements, as examples, include:

• INSERT − Used to add new data to a table.

• UPDATE − Used to modify existing data in a table.

• DELETE − Used to remove data from a table.

• SELECT − Used to retrieve data from one or more tables in a database.

Developers, analysts, and end users frequently utilise DML statements to alter data in a database. Users can use these statements to add, alter, or remove data from the database as necessary. Users can update data as necessary, delete out-of-date or unimportant material from the database, and retrieve specific data from a vast dataset using DML statements.

Uses of DML Commands

Following are the uses of DML commands:

• Data insertion − To add new data to a table in a database, DML operations like INSERT are employed. With this command, you can update records in a database.

• Data updating − To change current data in a table, DML operations like UPDATE are utilised. The values of particular columns in a table can be changed with the help of this command.

• Data deletion − To remove data from a table, use DML commands like DELETE. This command can be used to remove obsolete or pointless data from a database.

• Data retrieval − To get data from one or more tables in a database, DML operations like SELECT are employed.

• Filtering data − Data obtained by a SELECT statement is filtered using DML commands like WHERE. This command can be used to only retrieve the info that is relevant.

Differences: DDL and DML Commands in DBMS

The following table highlights the major differences between DDL and DML commands in DBMS:

Comparison Basis	DDL	DML
Basic	It deals with how data is stored in the database and aids in defining the structure or schema of a database.	It enables us to manipulate the data that is kept in the database, including retrieve, update, and delete.
Full-Form	Data Definition Language is the full name of this language.	Data Manipulation Language is the full name of this language.
Categorization	There is no additional categorisation for the DDL instructions.	The DML commands are divided into declarative and procedural (non-procedural) DMLs.
Command uses	The commonly used commands under DDL language are: CREATE DROP ALTER TRUNCATE RENAME	The commonly used commands under DML language are: INSERT UPDATE DELETE SELECT
Auto-commit	DDL commands automatically commit changes made to the database, making them permanent.	Database modifications are not irreversible since DML commands are not automatically committed.
Rollback	We cannot undo these statements since DDL instructions rendered the modifications permanent.	Because DML instructions do not permanently change the status of the data, they provide for the option of rollback.
WHERE clause	A WHERE clause is not used in DDL instructions since record filtration is not feasible in this situation.	DML statements allow the use of a WHERE clause while changing data in a database.
Effect	The entire database or table is impacted by the DDL command.	The DML commands will affect the single or multiple records based on the specified condition.

Conclusion

In conclusion, everybody dealing with databases has to understand the distinction between DDL and DML. The Data Definition Language, or DDL, is used to specify the architecture and structure of the database, including the creation of tables and changes to their characteristics. Data Manipulation Language, or DML, is used to insert, update, and delete records among other database-related operations.