About SQL
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
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:
1. DDL - Data Definition Language
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.
TRUNCATE : Remove all records from a table, including all spaces allocated for the records are removed.
COMMENT: Add comments to the data dictionary.
RENAME: Rename an object existing in the database
2. DML - Data Manipulation Language
SELECT : Retrieves certain records from one or more tables
INSERT : Creates a record
UPDATE : Modifies records
DELETE : Deletes records
3. DCL - Data Control Language
GRANT : Gives a privilege to user
REVOKE : Takes back privileges granted from user
4. TCL - Transaction Control Language
COMMIT : commits a Transaction.
ROLLBACK : rollbacks a transaction in case of any error occurs.
SAVEPOINT : sets a savepoint within a transaction.
SET TRANSACTION : specify characteristics for the transaction.
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
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:
1. DDL - Data Definition Language
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.
TRUNCATE : Remove all records from a table, including all spaces allocated for the records are removed.
COMMENT: Add comments to the data dictionary.
RENAME: Rename an object existing in the database
2. DML - Data Manipulation Language
SELECT : Retrieves certain records from one or more tables
INSERT : Creates a record
UPDATE : Modifies records
DELETE : Deletes records
3. DCL - Data Control Language
GRANT : Gives a privilege to user
REVOKE : Takes back privileges granted from user
4. TCL - Transaction Control Language
COMMIT : commits a Transaction.
ROLLBACK : rollbacks a transaction in case of any error occurs.
SAVEPOINT : sets a savepoint within a transaction.
SET TRANSACTION : specify characteristics for the transaction.