Data Manipulation Language (DML) in SQL

Definition: DML is a subset of SQL (Structured Query Language) used for managing and manipulating data within relational databases.
Key Functions:
- INSERT: Adds new records to a table.
  - Syntax: INSERT INTO table_name (column1, column2) VALUES (value1, value2);
- UPDATE: Modifies existing records in a table.
  - Syntax: UPDATE table_name SET column1 = value1 WHERE condition;
- DELETE: Removes records from a table.
  - Syntax: DELETE FROM table_name WHERE condition;
- SELECT: Retrieves data from one or more tables.
  - Syntax: SELECT column1, column2 FROM table_name WHERE condition;
Usage Scenarios:
- Data Insertion: Adding new entries to a database, such as customer data in a CRM system.
- Data Modification: Updating information, like changing an employee's job title or salary.
- Data Deletion: Removing outdated or incorrect records, such as deleted users or obsolete products.
- Data Retrieval: Fetching specific data for reports or analysis.
Important Concepts:
- WHERE Clause: Used in UPDATE and DELETE to specify which records should be affected.
- Transaction Control: DML operations can be grouped into transactions to ensure data integrity. Common commands include:
  - COMMIT: Saves all changes made during the transaction.
  - ROLLBACK: Reverts changes made during the transaction if an error occurs.
Performance Considerations:
- Indexing: Improves the speed of data retrieval operations (SELECT) but can slow down INSERT, UPDATE, and DELETE.
- Batch Processing: Performing bulk data operations can enhance performance over single-row operations.
Safety Measures:
- Data Validation: Ensure data integrity before performing DML operations.
- Backup: Regularly back up data to prevent loss during manipulation.
Common DML Commands:
- SELECT * FROM employees; - Retrieves all records from the employees table.
- INSERT INTO employees (name, position) VALUES ('John Doe', 'Manager'); - Adds a new employee.
- UPDATE employees SET position = 'Senior Manager' WHERE name = 'John Doe'; - Updates John Doe's position.
- DELETE FROM employees WHERE name = 'John Doe'; - Removes John Doe from the records.

Understanding DML is essential for effective data management in SQL databases, facilitating the manipulation of data to meet various application needs.

Data Manipulation Language (DML) in SQL

DML is a subset of SQL dedicated to managing and manipulating data in relational databases.

Key Functions

INSERT: Adds new records to a specified table using the syntax: INSERT INTO table_name (column1, column2) VALUES (value1, value2);
UPDATE: Modifies existing records, following the syntax: UPDATE table_name SET column1 = value1 WHERE condition;
DELETE: Removes records from a table with the command: DELETE FROM table_name WHERE condition;
SELECT: Retrieves data from one or more tables, formatted as: SELECT column1, column2 FROM table_name WHERE condition;

Usage Scenarios

Data Insertion: Used for adding entries like customer information in systems such as CRM.
Data Modification: Involves updating information, like an employee's title or salary.
Data Deletion: Entails removing outdated records, such as inactive users or obsolete products.
Data Retrieval: Fetches specific information for reports and analysis.

Important Concepts

WHERE Clause: Essential in UPDATE and DELETE commands to target specific records for modification or removal.
Transaction Control: DML operations can be grouped as transactions to maintain data integrity, utilizing:
- COMMIT: Saves all changes made in a transaction.
- ROLLBACK: Undoes changes if errors occur during the transaction.

Performance Considerations

Indexing: Enhances data retrieval speed (SELECT) but may slow down INSERT, UPDATE, and DELETE operations.
Batch Processing: Performing bulk operations boosts performance compared to individual row operations.

Safety Measures

Data Validation: Ensures data integrity before executing DML commands.
Backup: Regular backups are crucial to prevent data loss during manipulation.

Common DML Commands

SELECT * FROM employees;: Retrieves all records from the employees table.
INSERT INTO employees (name, position) VALUES ('John Doe', 'Manager');: Adds a new employee named John Doe with the position Manager.
UPDATE employees SET position = 'Senior Manager' WHERE name = 'John Doe';: Updates John Doe's position to Senior Manager.
DELETE FROM employees WHERE name = 'John Doe';: Removes John Doe's record from the table.

Conclusion

Proficiency in DML is vital for effective data management within SQL databases, facilitating diverse data manipulation tasks to support various application requirements.