SQL Commands | The Data Analytics Notes

SQL commands are the fundamental building blocks used to communicate with a Database Management System (DBMS).
They help us interact with databases by performing specific operations and queries on data.

Categories of SQL Commands

SQL commands are mainly divided into five categories:

DDL — Data Definition Language

Used to define and modify the structure of database objects.

· CREATE — Creates a database or database objects (tables, views, etc.)

· DROP — Deletes objects from the database

· ALTER — Modifies the structure of an existing database object

· TRUNCATE — Removes all records from a table (cannot be rolled back)

· RENAME — Renames an existing database object

DQL — Data Query Language

Used to retrieve data from the database.

· SELECT — Retrieves data from one or more tables

DML — Data Manipulation Language

Used to manage data stored in tables.

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· INSERT — Adds new rows (records) to a table

· UPDATE — Modifies existing records in a table

· DELETE — Removes specific records from a table

DCL — Data Control Language

Used to control access and permissions in the database.

· GRANT — Provides user access privileges

· REVOKE — Removes user access privileges

TCL — Transaction Control Language

Used to manage transactions in the database.

· COMMIT — Saves all changes made during a transaction

· ROLLBACK — Reverts changes if an error occurs

· SAVEPOINT — Sets a point in a transaction to roll back to if needed

· SET TRANSACTION — Defines the properties of a transaction, such as isolation level and read/write mode, before it begins.

Takeaway

SQL commands form the foundation of working with databases. Understanding these categories helps us execute queries correctly and manage data effectively.

Next Up

Before implementing SQL commands, we’ll explore the SQL interface and understand how it is structured.