INFS1603 Lecture Notes - Lecture 7: Data Manipulation Language, Data Control Language, Sql

• School: UNSW, UNSW Sydney
• Department: Information Systems
• Course: INFS1603
• Professor: All

Document Summary

Dml: dml sql statements are used to retrieve and manipulate data from the database, dml sql statements are largely standardized and hence have only minor differences between sql variants, dml sql commands include the following, delete. Dcl: dcl sql statements control the security/permissions of the database, dcl sql statements are closely related to the dbms and hence have large differences between the sql variants, dcl sql commands include the following, grant, deny, revoke. Codd relation model is the conceptual basis for relational databases. The relational model includes two relational languages: relational calculus: a non-procedural, high-level language that provides a declarative way to specify database queries, relational algebra: procedural, low-level language that provides a procedural way for specifying queries. Cross join joins (creates and returns) the cartesian product of two relations r and s. Inner join returns combined tuples from r and s that fulfil a certain criterion.