DPC2007 MySQL Stored Routines for PHP Developers (Roland Bouman)

1Copyright 2007 MySQL AB The World’s Most Popular Open Source Database

Amsterdam, June 16 2007● MySQL: Quick Introduction● MySQL Stored Routines for PHP developers● Questions and Discussion


Roland Bouman (rpbouman.blogspot.com)Certification DeveloperMySQL AB, Leiden

● MySQL Community Contributor since 2005● Joined MySQL AB in July 2006

● Certification Developer:● MySQL 5.1 Cluster DBA exam (CMCDBA)● MySQL Associate exam (CMA)

● Attained:● CMDEV● CMDBA

● Formerly: Consultant & Application Developer (mostly Oracle, some MS SQL)




MySQL: Quick Introduction

● MySQL Software Products● RDBMS (Database)● Monitoring and Advisory Service ● Drivers and APIs● Client (GUI) Tools & Utilities

● MySQL Professional Services● Technical Support● Consulting● Training● Certification● Indemnification


● Generally Available, Stable Releases● MySQL 5.0 Server Community Edition

● Patches from community

● MySQL 5.0 Server Enterprise Edition● Stablility and Robustness, Early Bugfixes● Monitoring and Advisory Service● Binaries

● Development Releases:● MySQL 5.1 (New: Events, Partitioning)● MySQL 6.0 (New: Falcon)

● Other RDBMS Products: ● MySQL Cluster / Carrier Grade Edition● Embedded● MaxDB (SAP Certified)

MySQL Open Source RDBMS Products


MySQL Monitoring and Advisory Service


● For PHP● ext/mysql: “MySQL Functions”● ext/mysqli: “MySQL Improved Extension”● mysqlnd: “MySQL native driver for PHP”

● Beta 5.● Built Into PHP 5; PHP 6● Replaces libmysql

● Other:● ODBC: Connector/ODBC● JDBC: Connector/J● ADO.NET: Connector/.NET

MySQL Drivers and APIs




MySQL Stored Routines

● Overview of MySQL Stored Routines● MySQL Stored Routine Language● PHP Techniques● Use cases● Best Practices


MySQL Stored Routines● Overview of MySQL Stored Routines:

● Terminology, Purpose, Application

● MySQL Stored Routine Language● Block Structure, Parameters and Variables, Flow Control

Constructs, SQL inside stored routines.

● PHP Techniques● Creating and Calling Stored Procedures, Processing

Result set, Handling Multiple Result sets.

● Use cases● Best Practices

● What to do on the client, and what on the server● What to do in PHP, and what in Stored Routines.● Performance: how MySQL Stored Routines can help or

hurt performance.


MySQL Stored Routines: Overview● Programs as Database Schema Objects

● Executed in-process with the Database

● Types of Stored Routines:● Procedures● Functions● Triggers● Events (Temporal triggers; new in MySQL 5.1)

● Language: ● Subset of Standard SQL:2003 SQL/PSM● Procedural, Block structured● Do not confuse with User Defined Functions (UDF)!

● Available as of MySQL 5.0 (October 2005)


MySQL Stored Routine Types: Overview● Stored Procedures & Functions

● Encapsulate tasks or Calculations for reuse● Single point of definition for Business Logic● Source Safely stored and backed up● Added layer of Security

● Triggers● Data-Driven● Enforce Data quality through Basic validation● Enforce complex Business Rules● Automatically Update Aggregate tables

● Events (MySQL Server 5.1 beta)● Schedule Code Execution in time.

● Use instead of cron or windows event scheduler

● Automatically Update Aggregate tables


MySQL Stored Routines: Purpose / Advantages● Performance

● Save network roundtrips, lower latency

● Portability and Reuse● Single point of definition● Reusable from many application contexts

● Security● DEFINER versus INVOKER

● Grant only Execution Privilege

● Ease of Maintenance● Code stored in the database

● Browse using information_schema database

● 'Headless' administrative tasks● No additional runtime environment required


MySQL Stored Routines: Caveat / Disadvantages● Performance

● Overhead may result in higher latency● Increased usage of database server computing power may

negatively affect throughput

● Portability and Reuse● Which point of view?

● Database portability ?● Or Application portability?









● What to do on the client, and what on the server● What to do in PHP, and what in Stored Routines.● How MySQL Stored Routines can help or hurt

performance.


MySQL Stored Routine Language● Subset of Standard SQL “Persistent Stored

Modules” (SQL/PSM)● Procedural constructs with embedded SQL

● Parameters and (Local) variables● Manipulate values

● Statement Sequence● execute statements in order

● Choice● conditionally execute a particular sequence

● Repetition● execute a particular sequence multiple times

● A bit like Pascal with embedded SQL statements● Valid inside all stored routine types● Can be mixed with most SQL statements


Creating a MySQL Stored Procedure

CREATE PROCEDURE sp_hello( p_who VARCHAR(32))SELECT CONCAT('Hello, ',v_what,'!!');

• CREATE PROCEDURE DDL statement

• Created in the current schema (= database)• Name (sp_hello) must be unique with in the

schema, may be qualified (my_db.sp_hello)

• Parameter (p_who): IN parameter by default

• Procedure body is one single statement, in this case, an ordinary SQL SELECT statement.

• Prerequisite: CREATE ROUTINE and ALTER ROUTINE privileges


Calling a MySQL Stored Procedure

CALL sp_hello('PHP');

• CALL statement

• Name identifies the procedure within the schema, and maybe qualified: CALL my_schema.sp_hello('PHP')

• Must pass a parameter value

Result:

Hello, PHP!

• Result set returned to the client

• Prerequisite: EXECUTE ROUTINE privilege


Generic Statement Sequence: BEGIN...END

CREATE PROCEDURE sp_greating( p_who VARCHAR(32), p_what VARCHAR(32))BEGIN SELECT CONCAT('Hello ', p_who); SELECT CONCAT(p_what,'!');END

• BEGIN...END is a compound statement; it may contain multiple other statements.

• Contained statements executed Sequentially (in order of appearance)

• (Sidenote: 2 result sets are returned to the client)


Variables and Parameters

CREATE PROCEDURE sp_fibonacci( INOUT p_m INT, INOUT p_n INT, OUT p_s DOUBLE) BEGIN DECLARE v_m INT DEFAULT COALESCE(p_m,0); DECLARE v_n INT DEFAULT COALESCE(p_n,1);

SET p_m := v_n; single assignment SET p_n := v_m + v_n multiple , p_s := p_m/p_n; assignments

SELECT p_m, p_n, p_s;END;

• IN, OUT and INOUT parameters• DECLARE local variables, optionally assign a default value

• Use SET to assign values to one or more variables


Variables and Parameters

call sp_fibonacci(@m,@n,@s);++++| p_m | p_n | p_s |++++| 1 | 1 | 1 |++++call sp_fibonacci(@m,@n,@s);++++| p_m | p_n | p_s |++++| 1 | 2 | 0.5 |++++call sp_fibonacci(@m,@n,@s);++++| p_m | p_n | p_s |++++| 2 | 3 | 0.666666666 |++++


Variable Scope / Visibility

BEGIN DECLARE v_script, v_http VARCHAR(32); SET v_script := 'PHP', v_http := 'Apache'; SELECT v_script, v_http; BEGIN DECLARE v_http VARCHAR(32); SET v_http := 'lighttpd'; SELECT v_script, v_http; END; SELECT v_script, v_http;END;

• Variables are visible only inside the declaring block• Nearest Scope: inner declarations mask outer ones


Choice Constructs

● Compound statements● IF...END IF statement

● Simple test of a single condition● Conditionally start a sequence of statements (branch)● Optionally, chooses between two branches

● Don't confuse with the IF() function!

● CASE...END CASE statement● Conditionally starts one out of multiple branches

● Simple CASE statement

● Just like switch in PHP

● Searched CASE statement

● Just like nested if...elseif...else in PHP

● Don't confuse with the CASE..END expression!


Syntax: IF...END IF● Tests condition, branches when TRUE

● Conditional branch can contain a sequence

//main, unconditional branchIF <condition> THEN <statements> “true” branchEND IF;

● Optionally, include a branch for the other case:

IF <condition> THEN <statements> ”true” branchELSE <statements> ”false” branchEND IF;


IF CURRENT_TIME < '12:00:00' THEN SELECT 'Good Morning';ELSE SELECT 'Good Afternoon';END IF;

IF statement vs IF function

SELECT IF(CURRENT_TIME < '12:00:00' , 'Good Morning' , 'Good Afternoon' );

● An IF statement chooses between sequences of statements

● IF function chooses between expressions


Syntax: Simple CASE..END CASE● Evaluate expression and compare● Conditional branch can contain a sequence ● Optional ELSE branch

● Just like switch...case in PHP

CASE <expression> WHEN <expression1> THEN <statements> WHEN <expression2> THEN <statements> ELSE <statements> END CASE;


Syntax: Searched CASE..END CASE● Search first TRUE condition, then branch

● Conditional branch can contain a sequence ● Optional ELSE branch

● Just like if...elsif...else in PHP

CASE WHEN <condition> THEN <statements> WHEN <expression> THEN <statements> ELSE <statements> END CASE;


Repetition● Unstructured Loop

● No explicit logic to end the loop

● Structured● Logic to end the loop is part of the construct

LOOP <statement> END LOOP;

WHILE <condition>DO <statement>END WHILE;

REPEAT <statement>UNTIL <condition>END REPEAT;

● Iterate: ● Leave: exit the current block


TriggersCREATE [DEFINER = { <username> | CURRENT_USER }]TRIGGER <triggername> {BEFORE | AFTER} {INSERT | UPDATE | DELETE}ON <tablename>FOR EACH ROW <singlestatement>

● Automatically executed in response to row-level events occurring on table

● Can refer to OLD and NEW pseudo-records● INSERT: NEW● DELETE: OLD● UPDATE: both OLD and NEW

● Executed as part of transaction


Event Scheduler (Temporal Triggers)● New in MySQL 5.1● Automatically executed according to time

schedule● Can be recurring● Can be scheduled to start in the future● Can be instructed to clean itself up







Result Set, Handling Multiple Result Sets.



performance.


PHP and MySQL Stored Routines● Two relevant PHP extensions● MySQL Functions (ext/mysql)

● CREATE PROCEDURE and CALL work fine

● Just use the PHP function mysql_query()

● However, obtaining a result set is impossible

● MySQL Improved extension (ext/mysqli)● use mysqli_query() for one result set

● For multiple resultsets, use● mysqli_multi_query()

● mysqli_use_result()

● mysqli_store_result()

● mysqli_next_result()

● mysqli_more_results()


mysql_query() and Stored Routines<?php $db = mysql_connect($host,$usr,$pwd); mysql_select_db('test',$db); $result = mysql_query( "CALL sp_hello('PHP')",$db ); $num_rows = mysql_affected_rows($db); echo '<br/>num: ', $num_rows; echo '<br/>msg: ', mysql_error($db); echo '<br/>no: ', mysql_errno($db);?>

num: 1msg: PROCEDURE test.sp_hello can't return a result set in the given context

no: 1312


mysqli_query() and Stored Routines<?php $db = mysqli_connect($host,$usr,$pwd); $db>select_db('test'); $result = mysqli_query( $db,"CALL sp_hello('PHP')" ); $row = mysqli_fetch_row($result); echo $row[0];?>

Hello, PHP!


Handling Multiple result sets<?php $db = mysqli_connect($host,$usr,$pwd); $db>select_db('test'); $db>multi_query( "CALL sp_greating('PHP','Good Morning')" ); while($result = $db>store_result()) { while ($row = $result>fetch_row()) { echo $row[0]; } $result>close(); $db>next_result(); }?>

Hello PHP, Good Morning!








● Use Cases● Best Practices


performance.


MySQL Stored Routine Use Cases● Stored Procedures

● subtypes and vertical partitioning● data intensive transformation

● Stored Functions● domain specific calculations● data transformation

● Triggers● Auditing● Automatically Aggregate tables

● Events● Logging status● Updating aggregate tables “Materialized views”● ETL processes








● Use Cases● Best Practices


performance.


MySQL Stored Procedures: Best Practices● Use pure SQL when you can● Use stored procedures for data-intensive

operations● Don't use stored procedures for complex

computation● Don't use stored procedures for single layer

encapsulation● Simple CRUD layers don't scale● Stored Procedure should add significant functionality

● Return multiple result sets from stored procedures to reduce network roundtrips


MySQL Triggers: Best Practices● Use triggers to enforce integrity of data● Using triggers does not mean the application can

forget about validation


Amsterdam, June 16 2007

● MySQL: Quick Introduction● MySQL Stored Routines for PHP developers● Questions and Discussion


Technology

DPC2007 MySQL Stored Routines for PHP Developers (Roland Bouman)