Working with Databases and MySQL

Working with Databases
and MySQL

2PHP Programming with MySQL, 2nd Edition
Objectives
In this chapter, you will:
• Study the basics of databases and MySQL
• Work with MySQL databases
• Define database tables
• Modify user privileges
• Work with database records
• Work with phpMyAdmin

Introduction to Databases
A database is an ordered collection of information
Each row is called a record.
A record in a database is a single complete set of
related information
Each column is called a field.
Fields are the individual categories of information
stored in a record

Introduction to Databases
(continued)
Figure 7-1 Employee directory database

Understanding Relational
Databases
Relational databases consist of one or more
related tables
A primary table is the main table in a relationship
that is referenced by another table
A related table (or “child table”) references a
primary table in a relational database
A primary key is a field that contains a unique
identifier for each record in a primary table

Understanding Relational
Databases (continued)
A primary key is a type of index, which makes
retrievals and sorting faster
A foreign key is a field in a related table that
refers to the primary key in a primary table
Primary and foreign keys link records across
multiple tables in a relational database

One-to-One Relationships
A one-to-one relationship exists between two
tables when a related table contains exactly one
record for each record in the primary table
Create one-to-one relationships to break
information into multiple, logical sets
Information in the tables in a one-to-one
relationship can be placed within a single table

One-to-One Relationships
(continued)
Figure 7-2 One-to-one relationship

One-to-Many Relationship
A one-to-many relationship exists in a relational
database when one record in a primary table has
many related records in a related table
Breaking tables into multiple related tables to
reduce redundant and duplicate information is
called normalization
Provides a more efficient and less redundant
method of storing this information in a database

(continued)
Figure 7-3 Table with redundant information

(continued)
Figure 7-4 One-to-many relationship

Many-to-Many Relationship
A many-to-many relationship exists in a
relational database when many records in one
table are related to many records in another table
A junction table creates a one-to-many
relationship for each of the two tables in a
many-to-many relationship
A junction table contains foreign keys from the two
tables

Working with Database
Management Systems
A database management system (or DBMS) is
an application or collection of applications used to
access and manage a database
A schema is the structure of a database including
its tables, fields, and relationships
A flat-file database management system is a
system that stores data in a flat-file format
A relational database management system (or
RDBMS) is a system that stores data in a
relational format

Management Systems (continued)
Figure 7-5 Many-to-many relationship

Important aspects of database management
systems:
The structuring and preservation of the
database file
Ensuring that data is stored correctly in a
database’s tables, regardless of the database
format
Querying capability

A query is a structured set of instructions and
criteria for retrieving, adding, modifying, and
deleting database information
Structured query language (or SQL) is a standard data
manipulation language used among many database
management systems
Open database connectivity (or ODBC) allows ODBC-
compliant applications to access any data source for which
there is an ODBC driver

Understanding MySQL Identifiers
An alias is an alternate name used to refer to a
table or field in SQL statements
MySQL stores each database in a directory of the
same name as the database identifier
Field and index identifiers are case insensitive on
all platforms

Understanding MySQL Identifiers
(continued)
Identifiers that must be quoted using the backtick,
or single quote, character (`)are
An identifier that includes any character except
standard alphanumeric characters, underscores
(_) or dollar signs ($)
Any identifier that contains one or more space
characters
An identifier that is a reserved word in MySQL
An identifier made entirely of numeric digits
An identifier that contains a backtick character

Getting Help with MySQL
Commands

Creating Databases
Use the CREATE DATABASE statement to create a
new database:
mysql> CREATE DATABASE vehicle_fleet;[ENTER]
To use a new database, select it by executing the
USE DATABASE statement

Selecting a Database
Use the DATABASE() function to return the name
of the currently active database
mysql> SELECT DATABASE();[ENTER]
View the available databases using the SHOW
DATABASES statement
mysql> SHOW databases;[ENTER]
Use the DROP DATABASE statement to remove all
tables and delete a database
mysql> DROP DATABASE database;

Defining Database Tables
Data types that are assigned to fields determine
how much storage space the computer allocates for
the data in the database
Choose the smallest data type possible for each
field

Defining Database Tables
(continued)

Creating Tables
Use the CREATE TABLE statement to create a
new table and define the column names and data
types for each column
mysql> CREATE TABLE vehicles
(license VARCHAR(10), make VARCHAR(25),
model VARCHAR(50), miles FLOAT,
assigned_to VARCHAR(40));[ENTER]

Viewing Table Structure
Use the DESCRIBE table_name statement to
view the structure of the table

Changing Table Field Names
Use the ALTER TABLE to change the name of an
existing field in a table using the following syntax
ALTER TABLE table_name ADD [COLUMN]
(column_name column_type [, column_name
column_type ...]);
In MySQL Monitor, enter the following:
mysql> ALTER TABLE vehicles ADD COLUMN
(model_year INT);[ENTER]

Modifying Column Types
Use the ALTER TABLE to rename columns of an
existing field in a table using the following syntax
ALTER TABLE table_name CHANGE [COLUMN]
column_name new_name column_type;
mysql> ALTER TABLE vehicles CHANGE COLUMN
miles mileage FLOAT;[ENTER]

Renaming Columns
Use the ALTER TABLE to rename columns using
the following syntax
ALTER TABLE table_name MODIFY [COLUMN]
column_name column_type;
mysql> ALTER TABLE vehicles MODIFY COLUMN
model_year SMALLINT;[ENTER]

Renaming Tables
Use the ALTER TABLE to change the name of an
existing table using the following syntax
ALTER TABLE table_name RENAME [TO]
new_name;
mysql> ALTER TABLE vehicles RENAME TO
company_cars;[ENTER]

Removing Columns
Use the ALTER TABLE to remove an existing field
from a table using the following syntax
ALTER TABLE table_name DROP [COLUMN]
column_name;
mysql> ALTER TABLE company_cars DROP
COLUMN
assigned_to;[ENTER]

Deleting Tables
Execute the DROP TABLE statement to remove all
data and the table definition from a database
DROP TABLE table;
In MySQL Monitor, enter the following at the
mysql> prompt:
mysql> DROP TABLE company_cars;[ENTER]
You must be logged in as the root user or have DROP
privileges to delete a table.

Modifying User Privileges
Privileges are actions and operations a user
can perform with a table or a database
For security purposes, user accounts should only
be assigned the minimum necessary privileges to
perform given tasks

Modifying User Privileges
(continued)

Granting Privileges
The syntax for the GRANT statement is:
GRANT privilege [(column)] [, privilege [(columns)]] ...
ON {table | * | *.* | database.*}
TO user [IDENTIFIED BY 'password'];
The GRANT statement creates the user account
if it does not exist and assigns the specified
privileges
If the user account already exists, the GRANT
statement just updates the privileges

Revoking Privileges
The syntax for the REVOKE statement is:
REVOKE privilege [(column)] [, privilege [(columns)]] ...
ON {table | * | *.* | database.*}
FROM user;
The REVOKE ALL PRIVILEGES statement
removes all privileges from a user account for a
specified table or database
You must be logged in with the root account or
have sufficient privileges to revoke privileges
from another user account

Adding Records
Use the INSERT statement to add individual
records to a table
The syntax for the INSERT statement is:
INSERT INTO table_name (column1, column2, …)
VALUES(value1, value2, ...);
The values entered in the VALUES list must
be in the same order in which you defined the
table fields
Specify NULL in any fields for which you do not
have a value

Adding Records (continued)
mysql> INSERT INTO company_cars(license,
model_year, make, model, mileage)
VALUES('CK-2987', 2009, 'Toyota',
'Corolla', 3508.4);[ENTER]

The LOAD DATA statement, with the full path and
name of a local text file, is used to add multiple
records to a table
LOAD DATA INFILE 'file_path' INTO TABLE
table_name (column1, column2, …);
Each record in the text file must be placed on a
separate line with a tab delimiter between each
field

If the column list is omitted, the values on each line
must be in the same order you defined the table
fields
Use consecutive tabs with nothing between them
to designate a column with no value
mysql> LOAD DATA INFILE 'company_cars.txt'
INTO TABLE company_cars;[ENTER]

The optional FIELDS TERMINATED BY clause of
the LOAD DATA statement allows you to change
the field separator to a character such as (~
or ,) instead of the default tab character
mysql> LOAD DATA INFILE 'company_cars.txt‘
INTO TABLE company_cars;[ENTER]

Retrieving Records
Use the SELECT statement to retrieve records
from a table:
SELECT criteria FROM table_name;
Use the asterisk (*) wildcard with the SELECT
statement to retrieve all fields from a table
To return multiple fields, separate field names with
a comma

Retrieving Records (continued)
mysql> SELECT model, mileage FROM
company_cars;[ENTER]

Using Aggregate Functions
Aggregate functions summarize data in record
sets rather than display the individual records
The COUNT() function is unique in that
The wildcard (*) can be used as a function argument
instead of a field name
The keyword DISTINCT can be used after the opening
parentheses
The DISTINCT keyword can also be used with the SELECT
statement to retrieve records with a unique value in the
WHERE clause

Using Aggregate Functions
(continued)
To retrieve aggregate values for groups of records,
use the GROUP BY clause and include the fields
that you use to group the records as part of the
query
mysql> SELECT model_year, AVG(mileage)
FROM company_cars GROUP BY
model_year;[ENTER]

Sorting Query Results
Use the ORDER BY keyword with the SELECT
statement to perform an alphanumeric sort of the
results returned from a query
mysql> SELECT make, model FROM inventory
ORDER BY make, model;[ENTER]

Sorting Query Results (continued)
To perform a reverse sort, add the DESC keyword
after the name of the field by which
you want to perform the sort
mysql> SELECT make, model FROM
company_cars ORDER BY make DESC,
model;[ENTER]

Filtering Query Results
The criteria portion of the SELECT statement
determines which fields to retrieve from a table
You can also specify which records to return by
using the WHERE keyword
mysql> SELECT * FROM inventory WHERE
make='Martin‘;[ENTER]

Filtering Query Results (continued)
Use the keywords AND and OR to specify more
detailed conditions about the records you want to
return
mysql> SELECT * FROM company_cars
WHERE model_year=2007 AND
mileage<60000;[ENTER]

Filtering Query Results (continued)
mysql> SELECT * FROM company_cars
WHERE make='Toyota’ OR
make='Honda‘ ORDER BY mileage ;[ENTER]

Updating Records
To update records in a table, use the UPDATE
statement
The syntax for the UPDATE statement is:
UPDATE table_name
SET column_name=value
WHERE condition;
The UPDATE keyword specifies the name of the
table to update
The SET keyword specifies the value to assign to
the fields in the records that match the condition in
the WHERE keyword

Updating Records (continued)
mysql> UPDATE company_cars SET mileage=368.2
WHERE make='Ford’ AND model='Fusion';
[ENTER]

Deleting Records
Use the DELETE statement to delete records in a
table
The syntax for the DELETE statement is:
DELETE FROM table_name
WHERE condition;
The DELETE statement deletes all records that
match the condition
To delete all the records in a table, leave off the
WHERE keyword

Deleting Records (continued)
mysql> DELETE FROM company_cars WHERE
model_year=2006 AND make='Honda'
AND model='Accord';[ENTER]
To delete all records from a table, omit the WHERE
clause

Working with Databases and MySQL

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