Phpugph Mysql v3

8/6/2019 Phpugph Mysql v3

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MySQL Database Essentials

Cherrie Ann B. Domingo, CCNAPresident, PHP User Group Philippines (PHPUGPH)


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O bjectives for the Session

Understand relational database conceptsIntroduce MySQL RDBMSRetrieve row and column data from tables with the SELECT statementUse DML statements INSERT, UPDATE, DELETEControl database transactions using C O MMIT and R O LLBACK statements


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Historical Roots of Databases

First applications focused on clerical tasks: order/entry processing, payroll,work scheduling and so on.

Small organizations keep track of their files using a manual file system(folders, filing cabinets whose contents were logically related)

As organizations grew and reporting requirements became more complex,keeping track of data in a manual file system became more difficult.

DP (data processing) Specialists were hired to computerize the manual filesystems

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Disadvantages of File Systems

Data redundancy and inconsistency

Difficulty in accessing data

Data isolation

Concurrent access anomalies

Security problems

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Database Management Systems vs. File Systems

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Database Systems Terms

Database - a collection of related data

Insta nc e - a collection of information stored in a database at a given pointin time

Schema - over -all design of a database

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Database Management System (DBMS)

consists of a collection of interrelated data and a collection of programsused to access the data

introduced to address the data -dependency problem and at the sametime remove unnecessary burdens from the application programmer

Primary goal of a DBMS is to provide a convenient and efficientenvironment for retrieving and storing information

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Functions of DBMS

Data definitionmust be able to accept data definitions (internal, external, conceptualschemas and all associated mappings) in source form and convert tothe appropriate object form (DDL)

Data Manipulationmust be able to handle requests from the user to retrieve and possiblyupdate existing data in the database or to add new data to the database(DML)

Data Security and Integrity must be able to monitor user requests and reject any attempts toviolate the security and integrity checks defined by the DBA

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Functions of DBMS

Data Recovery and Concurrency must have the capability to recover from or minimize the effects of asystem crash

Data dictionary management must provide a system database called database dictionary. It containsmetadata (data about data) or the definition of other objects in thesystem

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Advantages of DBMS

Data Consistency format (name and size) of data being stored

E asier use of data

a database system provides a user -friendly query language as part of thepackage

Less storagesince data redundancy is reduced if not eliminated, the database will occupyless storage space

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Disadvantages of DBMS

Complex require special skills to implement and use

E xpensive

since it is complex, it will require additional training to those who will makeuse of the system. Also, the design and implementation is not cheap

V ulnerablesince all data are stored in one central location, it is vulnerable to partial orcomplete destruction when a breakdown of hardware components occur

Incompatibility with other database systems

files created in one product are not easily transferred to another databaseproduct

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a popular open source RDBMSsource code is available under terms of the GNU General Public License, aswell as under a variety of proprietary agreementsowned and sponsored by a single for -profit firm,

the Swedish company MySQL AB, now a subsidiary of Sun Microsystems,which holds the copyright to most of the codebasecommonly used by free software projects which require a full -featureddatabase management system, such as WordPress, phpBB and othersoftware built on the LAMP software stack

also used in very high -scale World Wide Web productsincluding Google and Facebook

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open source tool written in PHP intended to handle the administrationof MySQL over the World Wide Webcan perform various tasks such as:

creating, modifying or deleting databases, tables, fields or rows

executing SQL statements; or managing users and permissions.

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ANSI standard for accessing database systems

used to retrieve, insert, update and delete records from a database

Works with database programs like MS Access, DB2, Informix, SQL Server, O racle,Sybase, etc.

SQL (Structured Query Language)

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SQLData Manipulation Language (DM L)

SelectUpdateDelete

Insert into

Data Definition Language (DD L)

Create tableAlter tableDrop tableCreate indexDrop index

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SQLData Control Language (DC L)

Rollback

Commit

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Capabilities of SELECT Statement

Selection - choose rows in a table that should be returned by a query

P rojection - choose columns in a table that should be returned by a query

Join - bring together data stored in different tables by creating a linkthrough a column that both tables share

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Capabilities of SELECT StatementS electionProjection

Table 1 Table 2

Table 1Table 1

Join

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SELECT Syntax

SELECT * | column_name(s)FROM table_name;

SELECT identifies the columns to be displayed

FROMidentifies the table containing those columns.

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Column Alias

Renames a column headingIs useful with calculationsImmediately follows the column name (There can also be the optionalA S keyword between the column name and alias.)

Requires double quotation marks if it contains spaces or specialcharacters or if it is case sensitive

SELECT column_name column_aliasFROM table_name;

SELECT column_name A S column_aliasFROM table_name;

*A multiple word headi ng c a n be spe c ified by putti ng it i n q uotes

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Arithmetic O perators

+ Addition- Subtraction/ Division* Multiplication% Modulo

SELECT ProductID, ProductName, UnitPrice * 10

FROM Products

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O perator Precedence

* / %+ -

Parentheses are used to force prioritized evaluation and to clarify statements

SELECT ProductName, UnitPrice*UnitsInStock+12

FROM Products

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Defining a NULL value

A null is a value that is unavailable, unassigned, unknown value orinapplicable

A null is not the same as a zero or blank space

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Null Values in Arithmetic Expressions

Arithmetic expressions containing a null value evaluate to null.

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Duplicate Rows

The default display of queries is all rows, including duplicate rows

To eliminate duplicate values, use DISTINCT keyword

SELECT DISTINCT department_idFROM employees;

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Displaying Table Structure

DESCRIBE | DESC- used to display table structure

Syntax:

DESC[RIBE] tablename

DESCRIBE employees

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Limiting rows that are selected

Restrict the rows that are returned by using the WH ERE clause

SELECT *|{[DISTINCT] column|expression [ alias ],...}FROM table[ WH ERE condition(s) ];

The WH ERE clause follows the FROMclause.

SELECT employee_id, last_name, job_id, department_id FROM employees

WHERE department_id = 90 ;

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Character Strings and Dates

Character strings and date values are enclosed in single quotation marks.Character values are case sensitive, and date values are format sensitive.

The default date format is YYYY -MM -DD.

SELECT last_name, job_id, department_id FROM employees

WHERE last_name = 'Whalen' ;

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Comparison ConditionOperator Meaning

= Equal to

> Greater than

>= Greater than or equal to

< Less than


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Using Comparison Conditions

SELECT last_name, salaryFROM employees

WHERE salary


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BETWEEN condition

Used to display rows based on a range of values

SELECT last_name, salaryFROM employees

WHERE salary B ETWEEN 2500 AND 3500 ;

Lower limit Upper limit

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IN condition

test for values in a list

SELECT employee_id, last_name, salary, manager_id FROM employees

WHERE manager_id IN (100, 101, 201) ;

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LIKE conditionUse the LIKE condition to perform wildcard searches of valid search stringvalues.

Search conditions can contain either literal characters or numbers:% denotes zero or many characters.

_ denotes one character.

SELECT first_nameFROM employees

WHERE first_name LIKE 'S%' ;

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LIKE condition

You can combine pattern -matching characters:

You can use the ESC A PE identifier to search for the actual % and _ symbols.

SELECT last_nameFROM employees

WHERE last_name LIKE '_o%' ;

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NULL Conditions

Test for nulls with the IS NULL operator

SELECT last_name, manager_id FROM employees

WHERE manager_id IS NULL ;

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LO GICAL Conditions

Operator Meaning

AND R eturns TRUE if both componentconditions are true

OR R eturnsTRUE

if ei th er componentcondition is true

NOT R eturns TRUE if the followingcondition is false

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Sorting using O RDER BY

Sort retrieved rows with the ORDER BY clause

A SC: ascending order, default

DESC: descending order

The ORDER BY clause comes last in the SELECT statement:

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O btaining Data from Multiple Tables

EMPLOYEES DEPARTMENTS

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Types of Joins

Joins that are compliant with the SQL:1999 standard include the following:

Cross joinsFull (or two -sided) outer joins

Arbitrary join conditions for outer joins

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JO INUsed to display data from multiple tables

EMPLOYEES DEPARTMENTS

Foreign key Primary key

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Qualifying Ambiguous Column Names

Use table prefixes to qualify column names that are in multiple tables.

Use table prefixes to improve performance.

Use column aliases to distinguish columns that have identical namesbut reside in different tables.

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Using Table Aliases

Use table aliases to simplify queries.Use table aliases to improve performance.

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Retrieving Records with the ON Clause

SELECT e.employee_id, e.last_name, e.department_id,d.department_id, d.location_id

FROM employees e JOIN departments d ON (e.department_id = d.department_id);

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Self -Joins Using the ONClause

MANAGER_ID in the WORKER table is equal toEMPLOYEE_ID in the MANAGER table.

EMPLOYEES (WORKER) EMPLOYEES (MANAGER)

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Self -Joins Using the ONClause

SELECT e.last_name emp, m.last_name mgrFROM employees e JOIN employees m ON (e.manager_id = m.employee_id);

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Inner J O IN

Inner Join - the typical join operation which uses some comparisonoperator like = or ). These include equi - joins and natural joins.

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O uter J O INcan be a left or a right outer joinspecified with one of the following sets of keywords when they arespecified in the FR O M clause

DEPARTMENTS EMPLOYEES

There are no employees indepartment 190.

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INNER Versus O UTER Joins

In SQL:1999, the join of two tables returning only matched rows iscalled an inner join.

A join between two tables that returns the results of the inner join as

well as the unmatched rows from the left (or right) tables is called aleft (or right) outer join.

A join between two tables that returns the results of an inner join aswell as the results of a left and right join is a full outer join.

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LEFTO UTER JO IN

SELECT e.last_name, e.department_id, d.department_nameFROM employees e LEFT OUTER JOIN departments d ON (e.department_id = d.department_id) ;

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FULLO UTER JO IN

SELECT e.last_name, d.department_id, d.department_nameFROM employees e FULL OUTER JOIN departments d ON (e.department_id = d.department_id) ;

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Cartesian Products

A Cartesian product is formed when:

A join condition is omittedA join condition is invalid

All rows in the first table are joined to all rows in the second table

To avoid a Cartesian product, always include a valid join condition.

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Generating a Cartesian Product

Cartesian product:20 x 8 = 160 rows

EMPLOYEES (20 rows) DEPARTMENTS (8 rows)

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Creating CR O SS JO IN

The CROSS JOIN clause produces the cross -product of two tables.

This is also called a Cartesian product between the two tables.

SELECT last_name, department_nameFROM employeesCROSS JOIN departments ;

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Adding a New Row to a TableDEPARTMENTS Newrow

Insert new rowinto theDEPARTMENTS table

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INSERT statement

Add new rows to a table by using the INSERT statement:

With this syntax, only one row is inserted at a time.

INSERT INTO table [( column [ , column... ])] VALUES (value [ , value... ]);

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Inserting New Rows Insert a new row containing values for each column. List values in the default order of the columns in the table. O ptionally, list the columns in the INSERT clause.

Enclose character and date values in single quotation marks.

INSERT INTO departments(department_id,department_name, manager_id, location_id)

VALUES (70, 'Public Relations', 100, 1700);1 row created.

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UPDA TE Statement Syntax

Modify existing rows with the UPDA TE statement:

Update more than one row at a time (if required).

UPDATE tableSET column = value [, column = value, ... ][WHERE condition ];

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Updating Rows in a Table

Specific row or rows are modified if you specify the WH ERE clause:

All rows in the table are modified if you omit the WH ERE clause:

UPDATE employeesSET department_id = 70

WHERE employee_id = 113;1 row updated.

UPDATE copy_empSET department_id = 110;22 rows updated.

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Removing a Row from a Table

Delete a row from the DEPARTMENTStable:

DEPARTMENTS

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DELETE Statement

You can remove existing rows from a table by using the DELETEstatement:

DELETE [FROM] table

[WHERE condition ];

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Deleting Rows from a Table

Specific rows are deleted if you specify the WHERE clause:

All rows in the table are deleted if you omit the WHEREclause:

DELETE FROM departments WHERE department_name = 'Finance';1 row deleted.

DELETE FROM copy_emp;22 rows deleted.

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TRUNCATE Statement

Removes all rows from a table, leaving the table empty and the tablestructure intactIs a data definition language (DDL) statement rather than a DMLstatement; cannot easily be undone

Syntax:

Example:

TRUNCATE TA B LE table_name ;

TRUNCATE TA B LE copy_emp;

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DRO P Statement

All data and structure in the table are deleted.Any pending transactions are committed.All indexes are dropped.All constraints are dropped.

You cannot roll back the DROP T A BLE statement.

DROP TA B LE dept80;Table dropped.

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Database Transactions

A database transaction consists of one of the following:DML statements that constitute one consistent change to the dataO ne DDL statementO ne data control language (DCL) statement

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Database Transactions

Begin when the first DML SQL statement is executedEnd with one of the following events:

A COMMIT or ROLLBA CK statement is issued.

A DDL or DCL statement executes (automatic commit).The system crashes.

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Advantages of COMMITand ROLLBA CK Statements

With COMMITand ROLLBA CK statements, you can:

Ensure data consistencyPreview data changes before making changes permanent

Group logically related operations

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Controlling Transactions

DELETE

INSERT

UPDATE

INSERT

COMMIT T ime

T ransaction

ROLLB ACK

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State of the Data Before COMMITor ROLLBA CK

The previous state of the data can be recovered.The current user can review the results of the DML operations by usingthe SELECT statement.O ther users cannot view the results of the DML statements by the

current user.The affected rows are locked ; other users cannot change the data inthe affected rows.

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State of the Data After COMMITData changes are made permanent in the database.The previous state of the data is permanently lost.All users can view the results.Locks on the affected rows are released; those rows are available for

other users to manipulate.

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Committing Data

Make the changes:

Commit the changes:

DELETE FROM employees WHERE employee_id = 99999;

1 row deleted.

INSERT INTO departments VALUES (290, 'Corporate Tax', NULL, 1700);

1 row created.

COMMIT;Commit complete.

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State of the Data After ROLLBA CKDiscard all pending changes by using the ROLLBA CKstatement:

Data changes are undone.Previous state of the data is restored.

Locks on the affected rows are released.

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State of the Data After ROLLBA CK

DELETE FROM test;25,000 rows deleted.

ROLLB ACK;Rollback complete.

DELETE FROM test WHERE id = 100;1 row deleted.

SELECT * FROM test WHERE id = 100; No rows selected.

COMMIT;Commit complete.

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SummaryThis session covers the following topics:

RDBMS concepts

Selecting all data from different tablesDescribing the structure of tablesPerforming arithmetic calculations and specifying column names

Use of the statements below:

F unction Description

INSERT Adds a new row to the table

UPDATE Modifies existing rows in the table

DELETE R emoves existing rows from the tableCOMMIT Makes all pending changes permanent

ROLLB ACK Discards all pending data changes


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Presentation Slides ^___^

Y ou may get the copy fromhttp://www.slideshare.net/cherrieanndomingo/php -roadshow -mysql -database -essentials


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Contact Me ^__^

Cherrie Ann B. Domingo, CCNA

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cherrie.ann.domingo

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http://www.plurk.com/chean

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[email protected]

[email protected]

http://www.cherrieanndomingo.com

+63917.865.2412/+63915.441.0707

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