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Navigating MySQL StoredProcedures & Functions and

TriggersPresented by:

Sheeri K. Cabral

At ODTUG Kaleidoscope 2010

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200!"2010 Pythian

Who I Am

● MySQL DBA

●

MySQL ser !rou"

● First #rac$e A% Director 'or MySQL

● Lots o' community stu'' (videos) *$og) "odcast on hiatus+

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,tended SQL Synta,●

No "$-s.$

● Stored /outines

 – Stored "rocedures – Stored 'unctions

● 0ie1s

● Triggers

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Triggers●

Invo2ed automatica$$y

● BF#/) AFT/

● INS/T) PDAT) DLT

● 3 triggers "er ta*$e

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Data %hanges 1-out Triggering

● T/N%AT

● D/#P

● Foreign 2ey cascading actions

 –

Fi,ed 1hen 'oreign 2eys in a$$ storage engines – Sti$$ in the distance

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Data %hanges that Trigger 

● /PLA%

 –  A$1ays INS/T) sometimes DLT too

● INS/T444#N DPLI%AT 56 PDAT

 – INS/T ,or PDAT

● L#AD DATA INFIL

 – insert

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%reating a trigger ●

T/I!!/ "rivi$ege – g$o*a$) d*) t*$

 – di''erent *e'ore MySQL 74843

CREATE TRIGGER trg_name[ BEFORE | AFTER ]

[ INSERT | UPDATE | DELETE ]

ON tbl_nameFOR EACH RO !!!!

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%on'$icts●

Same trigger nameERROR "#$% &H'((()* Tr+gger alrea,- e.+/t/

● Same com*ination o'9

 – BF#/ - AFT/

 – INS/T - PDAT - DLT

ERROR "0#$ &10((()* T2+/ 3er/+4n 45 6-S7L

,4e/n8t -et /9::4rt 8m9lt+:le tr+gger/ ;+t2 t2e/ame a

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Sam"$e Trigger 

CREATE TRIGGER /ta55_9:,ate_,ate

BEFORE INSERT ON /ta55

FOR EACH RO

SET NE!

● NW : a$ias 'or ne1 ro1(s+ inserted

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NW and #LD a$iases●

NW – BEFORE INSERT

 – BEFORE UPDATE

●

#LD – AFTER UPDATE

 – AFTER DELETE

● N#N

 – AFTER INSERT

 – BEFORE DELETE

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Dro""ing a Trigger 

● DROP TRIGGER trg_name>

● DROP TRIGGER IF E?ISTS trg_name>

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Mu$ti"$e SQL statements

● For triggers and others

● Wi$$ *e using ; – So set DLIMIT/ 'irst

● @ FOR EACH RO BEGIN @ END

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Mu$ti"$e SQL Statements

DELIMITER |

CREATE TRIGGER be54re_/ta55_+n/ert

BEFORE INSERT ON /ta55

FOR EACH RO BEGIN

INSERT INTO /ta55_

END |

DELIMITER ;

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%hanging a Trigger 

● No ALT/ T/I!!/

SELECT FRO6INFOR6ATION_SCHE6A!TRIGGERS HERETRIGGER_SCHE6A=8,b_name8 ANDTRIGGER_NA6E=8trg_name8

SHO CREATE TRIGGER trg_name>

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Triggers on S"ecia$ Ta*$es

● Triggers are not su""orted on9

 – 0ie1s – Tem"orary ta*$es

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Trigger /untime Behavior 

● s.$

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Permissions

CREATE DEFINER=[ 9/er24/t | CURRENT_USER&) ]

TRIGGER trg_name

[ BEFORE | AFTER ] [ INSERT|UPDATE|DELETE]

ON tbl_name FOR EACH RO BEGIN @ END>

● /e.uires SP/ "rivi$ege to set 9/er24/t

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Finding Triggers

SELECT FRO6INFOR6ATION_SCHE6A!TRIGGERS HERETRIGGER_SCHE6A=8,b_name8>

SHO TRIGGERS>

SHO TRIGGERS FRO6 8,b_name8>

SHO TRIGGERS LIE 8trg_name8>

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Triggers and /e"$ication

● CREATEDROP TRIGGER not re"$icated

● Statement=*ased re"$ication

 –  Actions not saved to *inary $og – Put triggers on master and s$ave

● /o1=*ased re"$ication

 –

 A$$ changes are saved to *inary $og – Triggers on master on$y

● Mi,ed acts $i2e ro1=*ased

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Triggers %annot9

● Modi'y a ta*$e *eing used *y the DML 1ithoutNW or #LD a$iases

●

Be de'ined on a m-/l ta*$e● se SELECT 1ithout INTO 3ar+able_name

● se SHO commands

● se LOAD DATATABLE● se BACUPRESTORE DATABASE

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Triggers %annot9

● se "re"ared statement commands

PREPARE E?ECUTE DEALLOCATE PREPARE

● se FLUSH statements● Invo2e a DF to ca$$ an e,terna$ a""$ication

● se ALTER IE

● se RETURN

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Triggers cannot cause %#MMIT - /#LLBA%5

CO66IT

ROLLBAC

START TRANSACTION BEGIN BEGIN OR

LOC UNLOC TABLES

SET AUTOCO66IT="

TRUNCATE TABLE

Most ALTER CREATE DROP RENA6E stmts

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Stored /outines●

Per'ormance – %ached per connection

● Stored "rocedure

 – Ta2es in > or more args

 – #ut"uts a resu$t set

● Stored 'unction

 – Ta2es in > or more args

 – #ut"uts a sca$ar va$ue

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Simi$ar to Triggers

DELI6ITER |

CREATE PROCEDURE /t4re_455er+ng/

(IN p_store_id TINYINT UNSIGNED, OUT p_count INT UNSIGNED

SELECT COUNT&) INTO :_ |

DELI6ITER >

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No In"ut-#ut"ut

DELI6ITER |

CREATE PROCEDURE 9:,ate_all_/ta55_t+me &)

UPDATE /ta55

SET la/t_9:,ate=NO&) HERE "="> |

DELI6ITER >

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Invo2ing a Stored Procedurem-/l CALL /t4re_455er+ng/ &" /t4re_")>

79er- O ( r4;/ a55e

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Dro""ing a Stored Procedure

DROP PROCEDURE /t4re_455er+ng/>

DROP PROCEDURE IF E?ISTS/t4re_455er+ng/;

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Mu$ti"$e SQL statements

DELI6ITER |

CREATE PROCEDURE 9:,ate_all_/ta55_t+me &)

UPDATE /ta55

BEGIN

SET la/t_9:,ate=NO&) HERE "="> |

END

DELI6ITER >

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IN#T arguments

DELI6ITER |

CREATE PROCEDURE +n

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Loca$ varia*$es●

DECLARE 3ar ,ata_t-:e at *ody *eginningDELI6ITER |CREATE PROCEDURE :

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Stored Procedure /untime Behavior 

● s.$

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#ther o"tions (o"tiona$+● CO66ENT

● [ NOT ] DETER6INISTIC

● SQL usage

 –

6ODIFIES S7L DATA – READS S7L DATA

 – CONTAINS S7L

 – NO S7L

●  ALT/ P/#%D/ can change

 – DEFINER S7L SECURIT' CO66ENT

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Fu$$ %/AT P/#%D/ Synta,CREATE

[ DEFINER = 9/er24/t | CURRENT_USER M ]

PROCEDURE :_name & [ :arameter_l+/t ] )

[ 4:t+4n @ ]

BEGIN @ END● #"tion is one or more o'9

S7L SECURIT' DEFINER | INOERM

CO66ENT 8

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Stored Function● 0ery simi$ar to stored "rocedure

● #ut"ut is sca$ar on$y

 – #n$y IN "arameters) no IN#T or #T

●

Must use /T/NS c$ause – De'ines 1hat data ty"e 1i$$ *e returned

● Must use /T/N statement at end

 – To actua$$y return data

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,am"$e Stored FunctionDELI6ITER |

CREATE FUNCTION get_/t4re_+, &5_/ta55_+,TIN'INT UNSIGNED)

RETURNS TIN'INT UNSIGNED

BEGIN DECLARE 5_/t4re_+, TIN'INT UNSIGNED>

SELECT /t4re_+, INTO 5_/t4re_+, FRO6 /ta55HERE /ta55_+,=5_/ta55_+,>

RETURN 5_/t4re_+,>

END |

DELI6ITER >

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Invo2ing a Stored Function● No CALL $i2e stored "rocedure

● @ust as a regu$ar 'unction

m-/l SELECT get_/t4re_+,&")>JJJJJJJJJJJJJJJJJ| get_/t4re_+,&") |JJJJJJJJJJJJJJJJJ

| " |JJJJJJJJJJJJJJJJJ" r4; +n /et &(!(( /e

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Stored /outine rrors and Warnings

●  As i' statements 1ere run on command$ine

●

No indication o' 1hich $ine 'ai$ed

● No indication o' 1hich stored routine 'ai$ed

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%onditions and and$ers

DECLARE

CONTINUE | E?IT | UNDO M

HANDLER FOR

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cond

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,am"$eDELI6ITER |

CREATE PROCEDURE :

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%onditionsDECLARE

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St d / ti F$ % t $

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Stored /outine F$o1 %ontro$

CASE HEN

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Loo"s

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Loo"s

[label*] LOOP

/tatement_l+/t

END LOOP [label]

ITERATE label

LEAE label

%ursors

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%ursors

DECLARE

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DELI6ITER |CREATE PROCEDURE

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Questions) comments) etc● 0ie1s

● Post 1ith $in2s to "$ay-do1n$oad video)do1n$oad s$ides) notes9

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