Download SQL

What makes SQL so popular?
• Worldwide language of choice for DBMS
• Ease of use / English keyword-oriented
• Allows working with data to be logical without
having to worry about the details of retrieval or
manipulation. Limited statements but powerful.
• Portability – Compatible with other database
managers.
Why SQL…
• Powerful language for Set-At-A-Time
processing -- processes sets of data as groups
rather than as individual elements.
• Excellent tool for application development
• SQL is NOT an end user query product
(commands are simple but complex)
• Commonly used in HLL applications. (Embedded
SQL)
SQL Tasks
• Querying Data
• Inserting, updating, deleting rows in tables.
• Creating, replacing altering and dropping
objects.
• Controlling access to the database and it’s
objects.
• Guaranteeing database consistency and
integrity.
SQL is governed by the ANSI standards
committee. ANSI – http://www.ansi.org/
ALL major DBMS comply with ANSI
standards.
However each version provides it’s own set of
extensions that enhance the functionality of
the language. As a programmer be aware that
the use of the extensions makes the code less
portable.
(T-SQL, PL-SQL)
Four Types of SQL Statements
• Data Definition Language (DDL)
• Data Manipulation Language (DML)
• Data Control Language (DCL)
• Extensions of SQL, based on the
DBMS.
DDL-Used to create and management
database objects.
• CREATE
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Table
View
Trigger
Procedure
Indexes
User Defined Functions
• DROP
• ALTER
DML- Most commonly used component by
database developers.
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SELECT
INSERT
UPDATE
DELETE
DCL – Used to manage security in
databases.
• GRANT – Grant access to an object or a
statement.
• DENY – Used to deny any permission on
an object or statement.
• REVOKE – Removes any entry in the
permissions table (sys-permissions) that
GRANT or DENY use.
SQL Keywords Statements
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SELECT
FROM
DISTINCT
WHERE
HAVING
ORDER BY
GROUP BY
Aggregate Functions – COUNT, MAX, MIN, AVG, SUM
Control of Flow Statements
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IF … ELSE
RETURN
WAITFOR
WHILE
BREAK
CONTINUE
GOTO
Programming Conventions
• Use uppercase characters for all keywords
• Capitalize all table names and objects
• Use lowercase characters for all column
names and variables
• Include comments!!
• Keep names unique – Tables, Views, Stored
Procedures etc.
To CREATE a table called Test_table
We key in:
CREATE TABLE Test_table (
test_id
SMALLINT,
test_description VARCHAR(25) );
Data Types
String Data Types: CHAR (1-255)
NCHAR, NVARCHAR
TEXT
Numeric Data types: BIT (0,1)
DECIMAL (length varies)
INT (Integer, 2147483648)
SMALLINT (32767)
TINYINT (0-255)
To CREATE a table called Product
Key in:
CREATE TABLE Product (
pro_id Number,
pro_description
VARCHAR(25),
pro_cost CURRENCY,
Primary Key(pro_id));
To Delete a table called Product
Key in:
DROP TABLE Product
To change a table called Product
Key in:
ALTER TABLE Product
ADD Column prod_supplier TEXT(30);
ALTER TABLE Product
Alter Column prod_id Number;