Data Manipulation Language (DML) is a subset of SQL (Structured Query Language) used to manage and manipulate data within a database. With DML, users can insert, query, update, and delete data — essentially everything you'd typically do with data stored in a database.
| Command | Purpose |
|---|---|
SELECT |
Retrieve data from a table |
INSERT |
Add new data |
UPDATE |
Modify existing data |
DELETE |
Remove data |
-- Insert
INSERT INTO customers (name, city) VALUES ('Müller', 'Berlin');
-- Query
SELECT * FROM customers WHERE city = 'Berlin';
-- Update
UPDATE customers SET city = 'Hamburg' WHERE name = 'Müller';
-- Delete
DELETE FROM customers WHERE name = 'Müller';DML deals with the data inside tables, not with the structure of the tables themselves (that's handled by Data Definition Language, DDL).
DML operations can often be rolled back (undone), especially when transactions are supported.
In short: DML is the toolset you use to keep your database dynamic and interactive by constantly adding, reading, modifying, or deleting data.
DQL stands for Data Query Language, and it's a subset of SQL (Structured Query Language). It is used specifically to query data from a database without modifying it.
Read-only: DQL is used to retrieve data, not to insert, update, or delete it.
The primary command used is:
SELECTExample:
SELECT name, birthdate FROM customers WHERE city = 'Berlin';This command retrieves the names and birthdates of all customers living in Berlin — without changing any data.
| Sub-language | Meaning | Main Purpose |
|---|---|---|
| DQL | Data Query Language | Reading data |
| DML | Data Manipulation Language | Inserting, updating, deleting data (INSERT, UPDATE, DELETE) |
| DDL | Data Definition Language | Defining database structure (CREATE, ALTER, DROP) |
| DCL | Data Control Language | Managing access rights (GRANT, REVOKE) |
| TCL | Transaction Control Language | Handling transactions (COMMIT, ROLLBACK) |
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