COMP 5531
Introduction to MySQL
SQL
• SQL is a standard language for accessing and
managing databases.
• SQL stands for Structured Query Language.
What can SQL do?
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Retrieve data from a database.
Insert records in a database.
Update existing records.
Delete records.
Create new database.
Create new tables etc.
SQL Components
• SQL has three main parts.
– DDL (Data Definition Language)
• CREATE TABLE, DROP TABLE, ALTER TABLE
– DML (Data Manipulation Language)
• SELECT, INSERT, UPDATE, DELETE
– DCL (Data Control Language)
• GRANT, REVOKE
MySql
• Based on RDBMS. (Relational Database
Management System)
• The most popular Open Source SQL.
• Download link
– http://dev.mysql.com/downloads/
Manage Your Database
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CREATE DATABASE database_name;
SHOW DATABASES;
USE database_name;
DROP DATABASE database_name;
SHOW TABLES;
Create table
CREATE TABLE table_name
(
column_name1 data_type,
column_name2 data_type,
column_name3 data_type,
....
);
Data types
• Kind of values it can represent
Type
Description
INT
A standard integer
DECIMAL
A fixed-point number
CHAR
A fixed-length non-binary string
VARCHAR
A variable-length non-binary string
DATE
A date value in ‘YYYY-MM-DD’ format
TIME
A time value in ‘hh:mm:ss’ format
DATETIME
‘YYYY-MM-DD hh:mm:ss’ format
An example of Create Table
CREATE TABLE mytable
(Student_Id int,
LastName varchar(255),
FirstName varchar(255),
GPA decimal(3,2),
DOB date);
Managing the table
• DESC mytable;
• DROP TABLE mytable;
Inserting data into table
INSERT INTO table_name
VALUES (value1,value2,value3,...);
Or
INSERT INTO table_name (column1,column2,...)
VALUES (value1,value2,...);
Example of inserting data
insert into mytable values
(6246893,'Krishnan','Giri',3.44,'1987-03-03');
Viewing data in the table
SELECT column_name,column_name
FROM table_name;
And
SELECT * FROM table_name;
Example of viewing data
• select * from mytable;
• select student_id, gpa from mytable;
View data with a WHERE clause
• SELECT column_name,column_name
FROM table_name
WHERE column_name operator value
• select * from mytable
where student_id = 6246893;
Operators in the WHERE clause
Operator
Description
=
Equal
<>
Not equal
>
Greater than
<
Less than
>=
Greater than or equal
<=
Less than or equal
BETWEEN
Between an inclusive range
LIKE
Search for a pattern
IN
To specify multiple possible values for a
column
Select DISTINCT data
• SELECT DISTINCT column_name,column_name
FROM table_name;
• select distinct firstname from mytable;
SQL Constraints
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NOT NULL
UNIQUE
PRIMARY KEY
FOREIGN KEY
CHECK
DEFAULT