What is SQL?
SQL is Structured Query Language, which is a computer language for
storing, manipulating and retrieving data stored in relational database.
SQL is the standard language for Relation Database System.
All relational database management systems like MySQL, MS
Access, Oracle, Sybase, Informix, postgres and SQL Server use SQL
as standard database language. Also, they are using different dialects,
such as:
MS SQL Server using T-SQL,
Oracle using PL/SQL,
MS Access version of SQL is called JET SQL (native format) etc.
Why SQL?
Allows users to access data in relational database management
systems. Allows users to describe the data. Allows users to define
the data in database and manipulate that data. Allows to embed
within other languages using SQL modules, libraries & pre-compilers.
Allows users to create and drop databases and tables
Allows users to create view, stored procedure, functions in a database.
Allows users to set permissions on tables, procedures and views
SQL Commands:
The standard SQL commands to interact with relational databases are
CREATE, SELECT, INSERT, UPDATE, DELETE and DROP.
These commands can be classified into groups based on their nature:
, DDL - Data Definition Language: Command Description
CREATE Creates a new table, a view of a table, or other object in
database
ALTER Modifies an existing database object, such as a table.
DROP Deletes an entire table, a view of a table or other object in the
database.
DML - Data Manipulation Language:
Command Description INSERT Creates a record
UPDATE Modifies records
DELETE Deletes records
DCL - Data Control Language: Command Description
GRANT Gives a privilege to user
REVOKE Takes back privileges granted from user
DQL - Data Query Language: Command Description
SELECT Retrieves certain records from one or more tables
DBMS:
Database is a collection of related data and data is a collection of
facts and figures that can be processed to produce information.
A database management system stores data in such a way that it
becomes easier to retrieve, manipulate, and produce information.
3-tier Architecture
SQL is Structured Query Language, which is a computer language for
storing, manipulating and retrieving data stored in relational database.
SQL is the standard language for Relation Database System.
All relational database management systems like MySQL, MS
Access, Oracle, Sybase, Informix, postgres and SQL Server use SQL
as standard database language. Also, they are using different dialects,
such as:
MS SQL Server using T-SQL,
Oracle using PL/SQL,
MS Access version of SQL is called JET SQL (native format) etc.
Why SQL?
Allows users to access data in relational database management
systems. Allows users to describe the data. Allows users to define
the data in database and manipulate that data. Allows to embed
within other languages using SQL modules, libraries & pre-compilers.
Allows users to create and drop databases and tables
Allows users to create view, stored procedure, functions in a database.
Allows users to set permissions on tables, procedures and views
SQL Commands:
The standard SQL commands to interact with relational databases are
CREATE, SELECT, INSERT, UPDATE, DELETE and DROP.
These commands can be classified into groups based on their nature:
, DDL - Data Definition Language: Command Description
CREATE Creates a new table, a view of a table, or other object in
database
ALTER Modifies an existing database object, such as a table.
DROP Deletes an entire table, a view of a table or other object in the
database.
DML - Data Manipulation Language:
Command Description INSERT Creates a record
UPDATE Modifies records
DELETE Deletes records
DCL - Data Control Language: Command Description
GRANT Gives a privilege to user
REVOKE Takes back privileges granted from user
DQL - Data Query Language: Command Description
SELECT Retrieves certain records from one or more tables
DBMS:
Database is a collection of related data and data is a collection of
facts and figures that can be processed to produce information.
A database management system stores data in such a way that it
becomes easier to retrieve, manipulate, and produce information.
3-tier Architecture
