Unformatted text preview: SQL and Data Ret r ieval Overview
SQL AND DATA RETR I EVAL OVERV I EW
Up until now, we have been focused on analyzing the user's requirements and designing the
database. Now we are ready to start building our database and retrieving data from i t.
SQL (St ructured Query Language) is the "language" that we use to communicate with
t he database. Just as you speak in a particular language, the database receives requests in
SQL. At the basic level, SQL wri t ten for Access is very similar to SQL writ ten for Oracle or
SQL Server. More complex features of the language will vary more drastically from one
p rovider to another.
Th ree types of SQL
• D D L - ( Data Definition Language) is concerned with defining thestructure of the
database. This part of the language is used to create the database, tables and other
objects in the database. I t includes commands like C REATE and D ROP • D M L - ( Data Manipulation Language) is concerned with retrieving data, and
i nserting, updating and deleting data in the database. I t includes commands like
I NSERT, UPDATE, D E LE TE, SELECT. T his category includes D Q L (Data
Q uery Language) s tatements. • DCL - (Data Control Language) is concerned with control issues such as who are the
users and what operations can a particular user perform on the database. I t includes
commands like G RANT and REVOKE. O ptions for Executing SQL Commands:
1. I n teractive (dynamic)
o command line (character based), advantage-can run batches or scripts o Graphical User I nte rface (GU I) --advantage- easier to use, does not require
detailed syntax knowledge like command line interface 2. Embedded ...
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- Summer '10
- Databases, Query language, Data Control Language