IM02: Database Language
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This document discusses the different languages used to communicate with relational databases: DDL is used to define the database structure, DML manipulates data within schema objects like inserting and updating records, DCL controls user access privileges, and TCL manages transactions by committing or rolling back changes. It provides examples of commands for each type of language like CREATE and ALTER for DDL, SELECT and INSERT for DML, GRANT and REVOKE for DCL, and COMMIT and ROLLBACK for TCL.
IM02: Database Language
- 1. ELEMENTARY TO INFORMATION MANAGEMENT IM02: Database Language Presented by Kelvin Chan
- 2. Introduction • SQL is abbreviation for Structured Query Language • A Database Language that communicates with Relational Database • Can be divided into more specific language – DDL – DML – DCL – TCL
- 3. DDL • DDL is abbreviation for Data Definition Language • Used to define the database structure or schema • CREATE - to create objects in the database • ALTER - alters the structure of the database • DROP - delete objects from the database • TRUNCATE - remove all records from a table • COMMENT - add comments to the data dictionary • RENAME - rename an object
- 4. DML • DML is abbreviation for Data Manipulation Language • Used to manipulate data within schema objects • SELECT - retrieve data from the a database • INSERT - insert data into a table • UPDATE - updates existing data within a table • DELETE - deletes all records from a table, the space for the records remain • MERGE - UPSERT operation (Insert or Update) • CALL - call a Stored-Procedure
- 5. DCL • DCL is abbreviation for Data Control Language • Used to define roles and permissions to access database • GRANT - gives user's access privileges to database • REVOKE - withdraw access privileges given with the GRANT command
- 6. TCL • TCL is abbreviation for Transactional Control Language • Used to manage the changes made by DML statements • COMMIT - save work done ROLLBACK - restore database to original since the last COMMIT