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COMPUTER SOFTWARE APPLICATION - CITS




           REVOKE SELECT ON table_name FROM user_name;
           DCL commands play a crucial role in controlling who can access and manipulate data within a database, ensuring
           data integrity and security. Database administrators use these commands to define and enforce access policies,
           restrict unauthorized access, and manage the permissions of users and roles in the database system. Properly
           configured DCL commands help protect sensitive data and maintain the integrity of the database.
           TCL (Transaction Control Language)
           TCL, which stands for Transaction Control Language, is a subset of SQL (Structured Query Language) used for
           managing database transactions. Transactions in a database are sequences of one or more SQL statements that
           are treated as a single, indivisible unit of work. TCL commands are used to control the beginning and ending of
           transactions, ensuring data consistency and integrity. The primary TCL commands are:
           1  COMMIT:  The  COMMIT  command  is  used  to  permanently  save  the  changes  made  during  the  current
              transaction. Once a COMMIT is issued, all changes are made permanent and cannot be rolled back.
           COMMIT;

           2  ROLLBACK:  The  ROLLBACK  command  is  used  to  undo  changes  made  during  the  current  transaction
              and restore the database to its previous state. It cancels all the changes made since the last COMMIT or
              SAVEPOINT.
           ROLLBACK;
           3  SAVEPOINT: The SAVEPOINT command is used to set a point within a transaction to which you can later roll
              back if needed. It allows you to create intermediate savepoints within a transaction.

           SAVEPOINT savepoint_name;
           TCL commands are critical for maintaining data consistency and ensuring that a series of related SQL statements
           are executed as a single, atomic operation. Transactions help protect data integrity and ensure that the database
           remains in a consistent state even in the presence of errors or interruptions. The use of COMMIT and ROLLBACK
           commands is essential for managing the success or failure of database operations within a transaction.
           DQL(Data Query Language)
           Data Query Language (DQL) is a subset of SQL (Structured Query Language) specifically designed for retrieving
           and querying data from a relational database. DQL commands are used to interact with the data stored within
           database tables, allowing users to retrieve, filter, and manipulate data to extract meaningful information. The
           primary DQL command is:

           SELECT: The SELECT command is the core of DQL and is used to retrieve data from one or more tables in a
           database. It enables you to specify the columns you want to retrieve, apply filtering conditions, and sort the result
           set.
           SELECT column1, column2
           FROM table_name
           WHERE condition ORDER BY column1;
           In addition to SELECT, DQL may involve using clauses like WHERE to filter data, JOIN to combine data from
           multiple tables, GROUP BY for grouping data, HAVING for filtering grouped data, and more.
           DQL is fundamental for extracting and presenting data in a structured and meaningful way, making it one of the
           most commonly used components of SQL, especially for reporting and analysis purposes. It allows users to
           interact with and retrieve data from a database, helping them make informed decisions based on the information
           stored in the database.














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                              CITS : IT&ITES - Computer software application - Lesson 18 - 36
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