DPC2007 MySQL Stored Routines for PHP Developers (Roland Bouman)

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

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

Roland Bouman (rpbouman.blogspot.com)
Certification Developer
MySQL 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


MySQL Open Source RDBMS Products

● 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 Monitoring and Advisory Service


MySQL Drivers and APIs

● 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 Stored Routines

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


● Overview of MySQL Stored Routines:
● Terminology, Purpose, Application
● 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?


● PHP Techniques
● Use cases
● Best Practices
● 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
• Prerequisite: CREATE ROUTINE and ALTER ROUTINE
privileges
CREATE PROCEDURE sp_hello(
p_who VARCHAR(32)
)
SELECT CONCAT('Hello, ',v_what,'!!');

DDL statement
• CREATE PROCEDURE
• 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.

Calling a MySQL Stored Procedure

• Prerequisite: EXECUTE ROUTINE privilege
CALL sp_hello('PHP');

statement
• CALL
• 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


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

is a compound statement; it may
• BEGIN...END
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;
and INOUT parameters
• IN, OUT
• 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 |
++++
++++
| p_m  | p_n  | p_s  |
++++
|    1 |    2 |  0.5 |
++++
++++
| 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';
  END;
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 branch
IF <condition> THEN
  <statements>   “true” branch
END IF;

● Optionally, include a branch for the other case:
IF <condition> THEN
  <statements>   ”true” branch
ELSE
  <statements>   ”false” branch
END IF;


IF statement vs IF function
● An IF statement chooses between sequences of
statements
IF CURRENT_TIME < '12:00:00' THEN
  SELECT 'Good Morning';
ELSE
  SELECT 'Good Afternoon';
END IF;

function chooses between expressions
● IF
SELECT IF(CURRENT_TIME < '12:00:00'
       , 'Good Morning'
       , 'Good Afternoon'
       );


Syntax: Simple CASE..END CASE
● Evaluate expression and compare
● 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
● 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
LOOP
  <statement>
END LOOP;

● Structured
● Logic to end the loop is part of the construct
REPEAT
WHILE
  <statement>
  <condition>
UNTIL
DO
  <condition>
  <statement>
END REPEAT;
END WHILE;

● Iterate:
● Leave: exit the current block

Triggers
CREATE
  [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
both OLD and NEW
● UPDATE:
● 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


● PHP Techniques
Result Set, Handling Multiple Result Sets.
● Use cases
● Best Practices
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);
  $result = mysql_query(
    quot;CALL sp_hello('PHP')quot;,$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: 1
msg: 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,quot;CALL sp_hello('PHP')quot;
  );
  $row = mysqli_fetch_row($result);
  echo $row[0];
?>

Hello, PHP!


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

Hello PHP, Good Morning!


● PHP Techniques
● 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


● PHP Techniques
● 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


DPC2007 MySQL Stored Routines for PHP Developers (Roland Bouman)

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