Presentation slides of Sequence Query Language (SQL)

SQL
Structure Query Language
Represented By: Zain Raza
Discipline: Information Technology
5th Semester
Group # 8

Outlines
• What is SQL?
• What SQL Can do?
• Using SQL in Your Web Site
• SQL Statements
• Semicolon after SQL Statements?
• Important SQL Commands
• Create & Drop Database
• RDBMS
• keys
• Demo Database

What is SQL?
• SQL stands for Structured Query Language
• SQL is NOT case sensitive: select is the same as SELECT
• SQL lets you access and manipulate (handle or control) databases
• SQL is an ANSI (American National Standards Institute) standard

What SQL Can do?
• SQL can execute queries against a database
• SQL can retrieve data from a database
• SQL can insert records in a database
• SQL can update records in a database
• SQL can delete records from a database
• SQL can create new databases
• SQL can create new tables in a database
• SQL can create stored procedures in a database
• SQL can create views in a database
• SQL can set permissions on tables, procedures, and views
• there are different versions of the SQL language and they all support at least the major
commands (such as SELECT, UPDATE, DELETE, INSERT, WHERE) statements.

Using SQL in Your Web Site
To build a web site that shows data from a database, you will need:
• An RDBMS database program (i.e. MS Access, SQL Server, MySQL)
• To use a server-side scripting language, like PHP or ASP
• To use SQL to get the data you want
• To use HTML / CSS

SQL Statements
1- SELECT * FROM Customers;
2- SELECT column_name,column_name FROM table_name;
3- SELECT * FROM Customers WHERE Country='Mexico';
4- INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode,
Country)
VALUES ('Cardinal','Tom B. Erichsen','Skagen 21','Stavanger','4006','Norway');
5- UPDATE Customers
SET ContactName='Alfred Schmidt', City='Hamburg'
WHERE CustomerName='Alfreds Futterkiste';
6- DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste' AND
ContactName='Maria Anders';
7- SELECT * FROM Customers WHERE Country='Germany' AND City='Berlin';
8- SELECT * FROM Customers WHERE City='Berlin' OR City='München';

Semicolon after SQL Statements?
• Some database systems require a semicolon at the end of each
SQL statement.
• Semicolon is the standard way to separate each SQL statement in
database systems that allow more than one SQL statement to be
executed in the same call to the server.

Important SQL Commands
• 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
• CREATE DATABASE - creates a new database
• ALTER DATABASE - modifies a database
• CREATE TABLE - creates a new table
• ALTER TABLE - modifies a table
• DROP TABLE - deletes a table
• CREATE INDEX - creates an index (search key)
• DROP INDEX - deletes an index

SQL CREATE & Drop Database
Example:
If you want to create new database <testDB>, then CREATE DATABASE statement
would be as follows:
SQL> CREATE DATABASE testDB
Example:
If you want to delete an existing database <testDB>, then DROP DATABASE
statement would be as follows:
SQL> DROP DATABASE testDB;

RDBMS
• RDBMS stands for Relational Database Management System.
• RDBMS is the basis for SQL, and for all modern database systems
such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft
Access.
• The data in RDBMS is stored in database objects called tables.
• A table is a collection of related data entries and it consists of
columns and rows.

History of MySQL :
• MySQL is an open source SQL database, which is developed by Swedish company MySQL
AB. MySQL is pronounced "my ess-que-ell," in contrast with SQL, pronounced "sequel."
• MySQL is supporting many different platforms including Microsoft Windows, the major
Linux distributions, UNIX, and Mac OS X.
• MySQL has free and paid versions, depending on its usage (non-commercial/commercial)
and features. MySQL comes with a very fast, multi-threaded, multi-user, and robust SQL
database server. History:
• Development of MySQL by Michael Widenius & David Ax mark beginning in 1994.
• First internal release on 23 May 1995.
• Windows version was released on 8 January 1998 for Windows 95 and NT.
• Version 5.1: production release 27 November 2008.

Primary Key:
• A primary key is a field in a table which uniquely identifies each
row/record in a database table. Primary keys must contain unique
values. A primary key column cannot have NULL values.
• A table can have only one primary key, which may consist of single
or multiple fields. When multiple fields are used as a primary key,
they are called a composite key.
• If a table has a primary key defined on any field(s), then you can
not have two records having the same value of that field(s).

Create Primary Key :
• To create a PRIMARY KEY constraint on the "ID" column when
CUSTOMERS table already exists, use the following SQL syntax:
ALTER TABLE CUSTOMER ADD PRIMARY KEY (ID);

Delete Primary Key:
• You can clear the primary key constraints from the table, Use
Syntax:
• ALTER TABLE CUSTOMERS DROP PRIMARY KEY ;

Foreign Key:
• A foreign key is a key used to link two tables together. This is
sometimes called a referencing key.
• Foreign Key is a column or a combination of columns whose values
match a Primary Key in a different table.
• The relationship between 2 tables matches the Primary Key in one
of the tables with a Foreign Key in the second table.

Create foreign key :
• ALTER TABLE ORDERS
ADD FOREIGN KEY (Customer_ID) REFERENCES CUSTOMERS (ID)

Delete Foreign Key :
• To drop a FOREIGN KEY constraint, use the following SQL:
ALTER TABLE ORDERS
DROP FOREIGN KEY;

CHECK Constraint:
• The CHECK Constraint enables a condition to check the value being entered into
a record. If the condition evaluates to false, the record violates the constraint
and isn’t entered into the table. Example: For example, the following SQL
creates a new table called CUSTOMERS and adds five columns. Here, we add a
CHECK with AGE column, so that you can not have any CUSTOMER below 18
years:
CREATE TABLE CUSTOMERS(
ID INT NOT NULL,
NAME VARCHAR (20) NOT NULL,
AGE INT NOT NULL CHECK (AGE >= 18),
ADDRESS CHAR (25) ,
SALARY DECIMAL (18, 2),
PRIMARY KEY (ID)
);

How to add Check Constraint:
• ALTER TABLE CUSTOMERS
• MODIFY AGE INT NOT NULL CHECK (AGE >= 18 )

DROP a CHECK Constraint:
• To drop a CHECK constraint, use the following SQL. This syntax
does not work with MySQL:
ALTER TABLE CUSTOMERS
DROP CONSTRAINT myCheckConstraint;

SQL Operators :
• Operators are used to specify conditions in an SQL statement and
to serve as conjunctions for multiple conditions in a statement.
Arithmetic operators
Comparison operators
Logical operators

Presentation slides of Sequence Query Language (SQL)

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