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Data Definition Language (DDL):
Definition: DDL is used for defining and managing the structure of database objects like tables, indexes, and views.
Functions: It includes commands such as CREATE, ALTER, and DROP to create, modify, and delete database objects.
Data Manipulation Language (DML):
Definition: DML is used for managing data within database objects.
Functions: It includes commands such as SELECT, INSERT, UPDATE, and DELETE to retrieve, add, modify, and delete data.
Data Query Language (DQL):
Definition: DQL is used for retrieving information from a database.
Functions: It primarily consists of the SELECT statement, which is used to retrieve data from one or more tables.
Data Control Language (DCL):
Definition: DCL is used to control access to data within the database.
Functions: It includes commands such as GRANT and REVOKE to grant or revoke permissions on database objects.
Data Integrity:
Definition: Data integrity ensures the accuracy, consistency, and reliability of data stored in the database.
Functions: Techniques such as constraints (e.g., NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY), triggers, and rules are used to enforce data integrity.
Joins:
Definition: Joins are used to combine rows from two or more tables based on a related column between them.
Functions: Various types of joins such as INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN are used to retrieve data from multiple tables.
Indexes:
Definition: Indexes are data structures that improve the speed of data retrieval operations on database tables.
Functions: They are created on columns in database tables to facilitate faster retrieval of data by providing quick access paths to the data.
Transactions:
Definition: Transactions ensure the integrity of the database by allowing multiple SQL operations to be treated as a single unit of work that is either executed entirely or not at all.
Functions: Transactions ensure that the database remains in a consistent state, even in the event of failures or errors.
Stored Procedures and Functions:
Definition: Stored procedures and functions are sets of SQL statements that are stored in the database and can be executed as a single unit.
Functions: They provide modularity, reusability, and security by encapsulating complex logic within the database.
Views:
Definition: Views are virtual tables that are generated based on the result of a SELECT query.
Functions: They provide a way to simplify complex queries, restrict access to certain columns, and present data in a customized format without altering the underlying data.