17 January 2012 By Praveen Macherla 1,624 views No Comment
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1. Relational Database Management System (RDBMS)
- Software application that control the creation, maintenance, and use of a database.
- Based on the relational model.
- Data is stored in tables and the relationships among the data are also stored in tables.
- The data can be accessed or reassembled in many different ways without having to change the table forms.
2. Structured Query Language (SQL)
- Programming language designed for managing data in RDBMS.
- An RDBMS that runs as a server providing multi-user access to a number of databases.
- Popular open source database
- Used by a wide range of organizations to manage their data.
- Central component of the widely-used LAMP web application software stack — LAMP is an acronym for “Linux, Apache, MySQL, and PHP”.
4. SQL is a Standard
- Although SQL is an ANSI and ISO standard, there are many different versions of the SQL language.
- However, to be compliant with the standard, all RDBMS support at least the major commands (such as SELECT, UPDATE, DELETE, INSERT, WHERE) in a similar manner.
- Note: Almost all RDMS also have their own proprietary extensions in addition to the SQL standard!
5. SQL DDL and DML
- SQL can be categorized into: The Data Definition Language (DDL) and the Data Manipulation Language (DML).
- The DDL commands allow database tables to be created or deleted. It also defines indexes (keys), specifies links between tables, and imposes constraints between tables. The most important DDL statements in SQL are:
- CREATE DATABASE – creates a new database
- ALTER DATABASE – modifies a database
- DROP DATABASE – deletes a database
- CREATE TABLE – creates a new table
- ALTER TABLE – modifies a table
- DROP TABLE – deletes a table
- TRUNCATE TABLE – clear all rows/data in table and reset table counters
- RENAME TABLE – rename a table
- CREATE INDEX – creates an index (search key)
- DROP INDEX – deletes an index
- The query and update commands form the DML part of SQL:
- SELECT – extracts data from a database
- UPDATE – updates data in a database
- DELETE – deletes data from a database
- INSERT INTO – inserts new data into a database