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Writing Joins in MySQLPresented by:

Sheeri K. Cabral

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Topics CoveredJOINs

OUTER

LEFT, RIGHT, FULL OUTER

INNER

INNER, NATURAL, comma (,)

CROSS

Su!ueries

"E#EN"ENT SU$%UER&

"ERI'E" TA$LE

Ca*i* a su!uer+ o a JOIN

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E-amp.e/01ee2 iesive course

Home1or2 ever+ Frida+

Eac assi*me is /3 o4 +our *rade

Lo1es *rade is dropped

563 o4 +our *rade, oa.

7ee2.+ ess ever+ 8oda+

Same *radi* srucure as 18iderm 9 7ed: ;3 o4 +our *rade

Fia. e-am 9 Frida+ =3 o4 +our *rade

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Samp.e daa

1or2 a.eCREATE TABLE work (work_id tinyint(3) unsigned NOT NULL AUTO_INCREMENT,wn!e "r#$r(%&&) 'EAULT NULL,gi"en dte 'EAULT NULL,#t_o*_grde tinyint(3) unsigned NOT NULL,+RIMAR -E (work_id)) EN.INE/Inno'B 'EAULT C0AR1ET/2tin

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Samp.e daa!ys425 1ELECT 6 ROM work7

8999999999899999999989999999999998999999999999998: work_id : wn!e : gi"en : #t_o*_grde :8999999999899999999989999999999998999999999999998

: : $w : %;;9;9; : < :: % : test : %;;9;9;= : < :: 3 : $w% : %;;9;9;> : < :: = : test% : %;;9;9 : < :: & : $w3 : %;;9;9& : < :: < : test3 : %;;9;9> : < :: ? : !idter! : %;;9;9%; : & :: > : $w= : %;;9;9%% : < :: @ : test= : %;;9;9%& : < :: ; : $w& : %;;9;9%@ : < :: : test& : %;;9;%9; : < :: % : $w< : %;;9;%9;& : < :: 3 : test< : %;;9;%9;> : < :: = : *in2 : %;;9;%9% : %& :8999999999899999999989999999999998999999999999998

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Samp.e daasude a.e

CREATE TABLE student (student_id tinyint(3) unsigned NOT NULL AUTO_INCREMENTn!e "r#$r(%&&) 'EAULT NULL,e!i2 "r#$r(%&&) 'EAULT NULL,+RIMAR -E (student_id)) EN.INE/Inno'B 'EAULT C0AR1ET/2tin7

Eries

899999999999989999999999999999989999999999999999998: student_id : n!e : e!i2 :

899999999999989999999999999999989999999999999999998: : 1$eeri Cr2 : s$eeri*ooedu :: % : .iusee MDi : giusee*ooedu :: 3 : Co2in C$r2es : #o2in*ooedu :: = : Ron2d Brd*ord : ron2d*ooedu :899999999999989999999999999999989999999999999999998

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Samp.e daasude?1or2 a.e

Crete T2e CREATE TABLE student_work (student_id tinyint(3) unsigned NOT NULL,work_id tinyint(3) unsigned NOT NULL,grde_nu! tinyint(3) unsigned 'EAULT NULL,grde_2etter #$r(%) 'EAULT NULL,*or_grde enu!(FyF,FnF) 'EAULT FyF,-E student_id (student_id),-E work_id (work_id),CON1TRAINT student_work_i*k_ OREI.N -E (student_id)

REERENCE1 student (student_id),

CON1TRAINT student_work_i*k_% OREI.N -E (work_id)REERENCE1 work (work_id)) EN.INE/Inno'B 'EAULT C0AR1ET/2tin7

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Samp.e daasude?1or2 eries

IN1ERT INTO student_work (student_id,work_id,grde_nu!)GALUE1H9 1$eeri $d >> *or e#$ $wtest eD#et $w< (?%),H9 !idter! >>, *in2 @;, nd s$e did not tke test3(,,>>),(,%,>>),(,3,>>),(,=,>>),(,&,>>),(,?,>>),(,@,>>),(,;,>>),(,,>>),(,%,?%),(,3,>>),(,=,@;),H9 .iusee #o!2eted 22 ssign!entstests(%,,;;),(%,%,;;),(%,3,@;),(%,=,>>),(%,&,>>),(%,&),(%,?,@&),(%,>,;;),(%,@,;;),(%,;,>%),(%,,>&),

(%,%,>@),(%,3,@;),(%,=,@

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Samp.e daasude?1or2 eries

IN1ERT INTO student_work (student_id,work_id,grde_nu!)GALUE1H9 Co2in is usy 2nning %;; User Con*eren#e, ndH9 did not #o!2ete ny $w ssign!ents, nd s resu2tH9 did not do we22 on t$e tests(3,%,?&),(3,=,??),(3,@),(3,?,>&),(3,@,?%),(3,,>@),(3,3,?;),(3,=,>;)H9 Ron2d knew $is stu** ut got usy s t$e #ourseH9 went on(=,,;;),(=,%,;;),(=,3,@&),(=,=,@&),(=,&,@;),(=,,>&),(=,@,>&),(=,;,>;),(=,,>;),(=,%,?&),(=,3,?&),(=,=,>3)7

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Samp.e daaG.oa. *rade?um?.eer a.e

CREATE TABLE grde_nu!_2etter (grde_nu! tinyint(3) unsigned NOT NULL,grde_2etter #$r(%) NOT NULL 'EAULT FF,+RIMAR -E (grde_nu!)

) EN.INE/MyI1AM 'EAULT C0AR1ET/2tin7

!ys425 se2e#t !in(grde_nu!),!D(grde_nu!),#ount(6) *ro!grde_nu!_2etter78999999999999999989999999999999999899999999998: !in(grde_nu!) : !D(grde_nu!) : #ount(6) :

8999999999999999989999999999999999899999999998: ; : ;; : ; :8999999999999999989999999999999999899999999998 row in set (;;; se#)

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8+S%L JOINsA JOIN c.ause is opioa.

ON (.;:co.; .=:co.= AN" :::)

Ca a.so speci4+ .;:co.; e-pr, (.;:co.;B;6)

USING (co.;,co.=,:::)

Same as .;:co.;@.=:co.; AN" .;:co.=@.=:co.=

INNER, CROSS, comma (,) a.. do e same i*

As o4 8+S%L >:6, CO88A oi is .o1er

precedece a oer JOINS

SELECT:::FRO8 .;, .= ON (.;:co.@.=:co.)INNER JOIN .5 ON (.=:co.@.5:co.) 7HERE.;:co.@.=:co.D

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CROSS JOIN

Caresia produc

A.. comiaios

1ELECT n!e, wn!eROM student CRO11 JOIN work7

Usua..+ o desired

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INNER JOIN

a.e ; over.ap a.e =

;:co.; ;:co.=@ =:co.=

;:co.5 =:co.; =:co.5

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CROSS, INNER are semaic

CROSS JOIN aci* as a INNER JOIN

1ELECT sgrde_nu!, ggrde_2etterROM student_work A1 sCRO11 JOIN grde_nu!_2etter A1 gON (sgrde_nu!/ggrde_nu!)7

INNER JOIN aci* as a CROSS JOIN1ELECT n!e, wn!e ROM student INNER JOINwork7

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I 4ac +ou do o eed eier

JOIN aci* as a INNER JOIN

1ELECT sgrde_nu!, ggrde_2etterROM student_work A1 sJOIN grde_nu!_2etter A1 gON (sgrde_nu!/ggrde_nu!)7

JOIN aci* as a CROSS JOIN1ELECT n!e, wn!e ROM student JOIN work7

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JOIN c.ause

ON () or USING(:::)

Ca speci4+ i e 7HERE c.ause

Same resu.s

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8+ $es #racices

"o use a comma o oi

Ue-peced eavior 1i oer JOINs i a !uer+

Never use JOIND a.1a+s use INNER JOIN orCROSS JOIN

7oever deu*s 1i.. 2o1 +our ieio

Use a JOIN c.ause isead o4 a 7HERE c.ause 8ore c.ear 1a is a 4i.er ad 1a is a oi

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OUTER JOIN

So1 a.. ro1s a mac o oe side

*e a.. *rades 4or es5

1ELECT n!e, wn!e, grde_nu!ROM student CRO11 JOIN workLET OUTER JOIN student_workU1IN. (student_id,work_id)

K0ERE wn!e/Ftest3F7

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OUTER JOIN

LEFT OUTER JOIN

RIGHT OUTER JOIN

OUTER is reduda

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LEFT JOIN, ic.usive

a.e ; over.ap a.e =

;:co.; ;:co.=@ =:co.=

;:co.5 =:co.; =:co.5

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LEFT JOIN, e-c.usive

a.e ; over.ap a.e =

;:co.; ;:co.=@ =:co.=

;:co.5 =:co.; =:co.5

::::7HERE =:co.; IS NULL

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FULL OUTER JOIN

"oes o e-is i 8+S%L

Ca e simu.aed

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FULL OUTER JOIN, ic.usive

a.e ; over.ap a.e =

;:co.= ;:co.;@ =:co.=

;:co.5 =:co.; =:co.5

SELECT FRO8 .; LEFT JOIN .= :::

UNION KALL FRO8 .; RIGHT JOIN .=

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FULL OUTER JOIN

I4 i is a.read+ i e 4irs resu., do o pu i i e

secod resu.

SELECT FRO8 .; LEFT JOIN .= :::

UNION ALL FRO8 .; RIGHT JOIN .=

7HERE .;:co. IS NULL

I e =d!uer+ i e uio, o.+ ro1s a ave omac i .; are a2e:

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FULL OUTER JOIN, e-c.usive

a.e ; over.ap a.e =

;:co.= ;:co.;@ =:co.=

;:co.5 =:co.; =:co.5

SELECT FRO8 .; LEFT JOIN .= :::7HERE .=:co.; IS NULLUNION ALL SELECT FRO8 .; RIGHT JOIN .= 7HERE .;:co. IS NULL

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NATURAL modi4ier

"oes o use a JOIN c.ause

JOIN c.ause is allmaci* 4ie.d ames

7or2s 4or

NATURAL JOIN

NATURAL LEFT JOIN

NATURAL RIGHT JOIN

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NATURAL JOIN e-amp.e

Isead o4

1ELECT n!e,grde_nu!ROM student INNER JOIN student_work U1IN.(student_id)K0ERE n!e/F1$eeri Cr2F7

7rie1ELECT n!e,grde_nu!ROM student NATURAL JOIN student_workK0ERE n!e/F1$eeri Cr2F7

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NATURAL JOIN *oe a1r+Havi* e same 4ie.d ames 1e e 4ie.ds areo e!ua.

1ELECT swgrde_nu!, gn2grde_2etter ROMstudent_work A1 sw INNER JOINgrde_nu!_2etter A1 gn2 U1IN. (grde_nu!)7

Is NOT e!uiva.e o

1ELECT swgrde_nu!, gn2grde_2etter ROMstudent_work A1 sw NATURAL JOINgrde_nu!_2etter A1 gn27

Tis is 1+ e 4ie.d is ca..ed 1or2:1ame

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Su!ueries

A su!uer+ is a !uer+ 1ii a !uer+

8ore aura. 1a+ o4 i2i* 4or procedura.i2ers

S%L is dec.araive, ad opimiMed a 1a+

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#rocedura. Ti2i*

Ho1 o *e e ames ad *rades 4or es;

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

Ge ames ad *rades

SELECT ame, *rade?um

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?um

sar 1i e oi a.e

FRO8 sude?1or2

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?um

FRO8 sude?1or2

*e e ame

INNER JOIN sude USING (sude?id)

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?um

FRO8 sude?1or2

INNER JOIN sude USING (sude?id)

$u o.+ *e es;

7HERE 1or2?id IN (SELECT 1or2?id FRO8 1or2

7HERE 1ame@es;)

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?um

FRO8 sude?1or2

INNER JOIN sude USING (sude?id)

7HERE 1or2?id IN (SELECT 1or2?id FRO8 1or27HERE 1ame@es;)D

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?um

FRO8 sude?1or2

INNER JOIN sude USING (sude?id)

7HERE 1or2?id IN (SELECT 1or2?id FRO8 1or27HERE 1ame@es;)D

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"ec.araive Ti2i* Ge e amesad *rades 4or es;

I ave 5 ses o4 daa

sude as e ame

sude?1or2 as e *rades

1or2 as e ame o4 e assi*me

SELECT ame, *rade?um FRO8 :::: 7HERE

1ame@es;

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"ec.araive Ti2i* Ge e amesad *rades 4or es;

sude ad sude?1or2 re.ae + sude?id

SELECT ame, *rade?um FRO8

sude INNER JOIN sude?1or2 USING(sude?id)

::::

7HERE 1ame@es;D

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Ge a.. *rades 4or es5

Sar 1i

SELECT ame, *rade?um FRO8::::

7HERE 1ame@es5D

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Ge a.. *rades 4or es5

7e 1a a .isi* 4or eac ro1 i 1or2 a*ais

eac ro1 i sude

SELECT ame, *rade?um

FRO8 sude CROSS JOIN 1or2

::::

7HERE 1ame@es5D

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Ge a.. *rades 4or es5

We want a listing for each row in work against

each row in student

7a 1e 1a, o o1 o *e i: Tas dec.araive

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Ge a.. *rades 4or es5

Grades mi* o e-is 4or a.. e ro1s

:::so 1e.. eed a ouer oi

Fi.. i e va.ues 4rom sude?1or2 4or e *radesa do e-is, oii* o sude?id ad 1or2?id

SELECT ame, *rade?um

FRO8 sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame@es5D

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"rop e .o1es es score

Ho1

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"rop e .o1es es score

For our purposes, NULL @ 6:

So 1e.. eed o 2eep e CROSS JOIN as i eprevious !uer+

SELECT ame, *rade?um

FRO8 sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id)

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"rop e .o1es es score

Ge a.. ess

SELECT ame, *rade?um

FRO8 sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame .i2e es?D

7e e-pec = ro1s reured::::

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"rop e .o1es es score

Ge miimum *rade 4rom a.. ess perperso

SELECT ame, mi(*rade?um)

FRO8 sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame .i2e es?

GROU# $& sude?idD

7e e-pec ro1s

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"rop e .o1es es score

Cover o a U#"ATE saeme:::::

SELECT ame, mi(*rade?um)

FRO8 sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame .i2e es?

GROU# $& sude?idD

Tis is ard

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"rop e .o1es es scoreNo1 add i e res:::

U#"ATE sude?1or2 as upd

INNER JOIN sude?1or2 as se. USING(sude?id, 1or2?id)

RIGHT JOIN sude USING (sude?id, 1or2?id)

CROSS JOIN 1or2

SET upd:4or?*rade@ 7HERE 1ame .i2e es?

AN" upd:*rade?um@mi(se.:*rade?um)

GROU# $& se.:sude?idD

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Ta does 1or2::::Someimes +ou eed a su!uer+:::::

U#"ATE sude?1or2

SET 4or?*rade@ 7HERECONCAT(sude?id,1or2?id) IN (SELECTCONCAT(sude?id,1or2?id) FRO8

sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame .i2e es?

GROU# $& sude?id)D

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Ta does 1or2 eier::::Someimes +ou eed o do i i ; !uer+

Someimes is o ecessar+, u more opima.

#ro.em is e mi(*rade?um)::::GROU# $&

So use a emporar+ a.e

CREATE TE8#ORAR& TA$LE *rade?o?dropSELECT mi(coa.esce(*rade?um,6)) FRO8

sude CROSS JOIN 1or2 LEFT JOIN sude?1or2USING (sude?id,1or2?id) 7HERE 1ame .i2ees? *roup + sude?idD

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Temporar+ a.e

CREATE TEM+ORAR TABLE grde_to_dro (

student_id tinyint unsigned not nu22,work_id tinyint unsigned de*u2t nu22,grde_nu! tinyint unsigned de*u2t nu22)7

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Temporar+ a.e

IN1ERT INTO grde_to_dro (student_id,grde_nu!)

1ELECT student_id,!in(#o2es#e(grde_nu!,;))ROM student CRO11 JOIN workLET JOIN student_work U1IN.(student_id,work_id)K0ERE wn!e 2ike Ftest_F.ROU+ B student_id7

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Temporar+ a.eU+'ATE grde_to_dro A1 gtd INNER JOINstudent_work A1 sw U1IN.(student_id,grde_nu!)

1ET gtdwork_id / swwork_id 7

U+'ATE student_work A1 sw INNER JOINgrde_to_dro A1 gtd U1IN.(student_id,work_id)1ET sw*or_grde/FnF 7

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Temporar+ a.e

Reet *or droing t$e 2owest $o!ework

'RO+ TABLE I EI1T1 grde_to_dro7

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8ore es pracices

EP#LAIN a.. +our !ueries, ad *e e es +pe

possi.e

Avoid JOIN is (ide- is, STRAIGHT?JOIN)

Tr+ o opimiMe su!ueries io JOINs i4 possi.e

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Tas i

%uesios

Commes

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01/29/10

01/29/10 1

Writing Joins in MySQLPresented by:

Sheeri K. Cabral

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2

Topics CoveredJOINs

OUTER LEFT, RIGHT, FULL OUTER

INNER

INNER, NATURAL, comma (,)

CROSS

Su!ueries

"E#EN"ENT SU$%UER&

"ERI'E" TA$LE

Ca*i* a su!uer+ o a JOIN

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3

E-amp.e/01ee2 iesive course

Home1or2 ever+ Frida+ Eac assi*me is /3 o4 +our *rade

Lo1es *rade is dropped

563 o4 +our *rade, oa.

7ee2.+ ess ever+ 8oda+

Same *radi* srucure as 1

8iderm 9 7ed: ;3 o4 +our *rade

Fia. e-am 9 Frida+ =3 o4 +our *rade

H1 due e 4irs da+ o4 c.ass, o1 crue.

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4

Samp.e daa

1or2 a.eCREATE TABLE work (work_id tinyint(3) unsigned NOT NULL AUTO_INCREMENT,wn!e "r#$r(%&&) 'EAULT NULL,gi"en dte 'EAULT NULL,#t_o*_grde tinyint(3) unsigned NOT NULL,+RIMAR -E (work_id)) EN.INE/Inno'B 'EAULT C0AR1ET/2tin

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5

Samp.e daa!ys425 1ELECT 6 ROM work7

8999999999899999999989999999999998999999999999998: work_id : wn!e : gi"en : #t_o*_grde :

8999999999899999999989999999999998999999999999998: : $w : %;;9;9; : < :: % : test : %;;9;9;= : < :: 3 : $w% : %;;9;9;> : < :: = : test% : %;;9;9 : < :: & : $w3 : %;;9;9& : < :: < : test3 : %;;9;9> : < :: ? : !idter! : %;;9;9%; : & :: > : $w= : %;;9;9%% : < :: @ : test= : %;;9;9%& : < :: ; : $w& : %;;9;9%@ : < :: : test& : %;;9;%9; : < :: % : $w< : %;;9;%9;& : < :

: 3 : test< : %;;9;%9;> : < :: = : *in2 : %;;9;%9% : %& :8999999999899999999989999999999998999999999999998

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6

Samp.e daasude a.e

CREATE TABLE student (student_id tinyint(3) unsigned NOT NULL AUTO_INCREMENTn!e "r#$r(%&&) 'EAULT NULL,e!i2 "r#$r(%&&) 'EAULT NULL,+RIMAR -E (student_id)) EN.INE/Inno'B 'EAULT C0AR1ET/2tin7

Eries

899999999999989999999999999999989999999999999999998: student_id : n!e : e!i2 :899999999999989999999999999999989999999999999999998: : 1$eeri Cr2 : s$eeri*ooedu :: % : .iusee MDi : giusee*ooedu :

: 3 : Co2in C$r2es : #o2in*ooedu :: = : Ron2d Brd*ord : ron2d*ooedu :899999999999989999999999999999989999999999999999998

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7

Samp.e daasude?1or2 a.e

Crete T2e CREATE TABLE student_work ( student_id tinyint(3) unsigned NOT NULL, work_id tinyint(3) unsigned NOT NULL, grde_nu! tinyint(3) unsigned 'EAULT NULL, grde_2etter #$r(%) 'EAULT NULL, *or_grde enu!(FyF,FnF) 'EAULT FyF, -E student_id (student_id), -E work_id (work_id), CON1TRAINT student_work_i*k_ OREI.N -E (student_id)REERENCE1 student (student_id), CON1TRAINT student_work_i*k_% OREI.N -E (work_id)REERENCE1 work (work_id)) EN.INE/Inno'B 'EAULT C0AR1ET/2tin7

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8

Samp.e daasude?1or2 eries

IN1ERT INTO student_work (student_id,work_id,grde_nu!)GALUE1H9 1$eeri $d >> *or e#$ $wtest eD#et $w< (?%),H9 !idter! >>, *in2 @;, nd s$e did not tke test3(,,>>),(,%,>>),(,3,>>),(,=,>>),(,&,>>),(,?,>>),(,@,>>),(,;,>>),(,,>>),(,%,?%),(,3,>>),(,=,@;),H9 .iusee #o!2eted 22 ssign!entstests(%,,;;),(%,%,;;),(%,3,@;),(%,=,>>),(%,&,>>),(%,&),(%,?,@&),(%,>,;;),(%,@,;;),(%,;,>%),(%,,>&),(%,%,>@),(%,3,@;),(%,=,@

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Samp.e daasude?1or2 eries

IN1ERT INTO student_work (student_id,work_id,grde_nu!)GALUE1H9 Co2in is usy 2nning %;; User Con*eren#e, ndH9 did not #o!2ete ny $w ssign!ents, nd s resu2tH9 did not do we22 on t$e tests(3,%,?&),(3,=,??),(3,@),(3,?,>&),(3,@,?%),(3,,>@),(3,3,?;),(3,=,>;)H9 Ron2d knew $is stu** ut got usy s t$e #ourseH9 went on(=,,;;),(=,%,;;),(=,3,@&),(=,=,@&),(=,&,@;),(=,,>&),(=,@,>&),(=,;,>;),(=,,>;),(=,%,?&),(=,3,?&),(=,=,>3)7

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Samp.e daaG.oa. *rade?um?.eer a.e

CREATE TABLE grde_nu!_2etter ( grde_nu! tinyint(3) unsigned NOT NULL, grde_2etter #$r(%) NOT NULL 'EAULT FF, +RIMAR -E (grde_nu!)) EN.INE/MyI1AM 'EAULT C0AR1ET/2tin7

!ys425 se2e#t !in(grde_nu!),!D(grde_nu!),#ount(6) *ro!grde_nu!_2etter78999999999999999989999999999999999899999999998: !in(grde_nu!) : !D(grde_nu!) : #ount(6) :8999999999999999989999999999999999899999999998: ; : ;; : ; :8999999999999999989999999999999999899999999998

row in set (;;; se#)

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'e "ia*ram

a.e ; over.ap a.e =

;:co.; ;:co.=@ =:co.=

;:co.5 =:co.; =:co.5

Te over.ap is o.+ 1a is e!ua., eve ou* erema+ e = 4ie.ds 1i e same ame:

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8+S%L JOINsA JOIN c.ause is opioa.

ON (.;:co.; .=:co.= AN" :::) Ca a.so speci4+ .;:co.; e-pr, (.;:co.;B;6)

USING (co.;,co.=,:::)

Same as .;:co.;@.=:co.; AN" .;:co.=@.=:co.=

INNER, CROSS, comma (,) a.. do e same i*

As o4 8+S%L >:6, CO88A oi is .o1erprecedece a oer JOINS

SELECT:::FRO8 .;, .= ON (.;:co.@.=:co.)

INNER JOIN .5 ON (.=:co.@.5:co.) 7HERE.;:co.@.=:co.D

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CROSS JOIN

Caresia produc A.. comiaios

1ELECT n!e, wn!eROM student CRO11 JOIN work7

Usua..+ o desired

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INNER JOIN

a.e ; over.ap a.e =

;:co.; ;:co.=@ =:co.=

;:co.5 =:co.; =:co.5

So1 o.+ ro1s a maces o o sides Noe a e SELECT ma+ so1 e co.ums, u

e ve dia*ram is so1i* e matching:

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INNER JOIN

So1 o.+ ro1s a maces o o sides1ELECT sgrde_nu!, ggrde_2etterROM student_work A1 sINNER JOIN grde_nu!_2etter A1 g ON (sgrde_nu!/ggrde_nu!)7

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CROSS, INNER are semaic

CROSS JOIN aci* as a INNER JOIN1ELECT sgrde_nu!, ggrde_2etterROM student_work A1 sCRO11 JOIN grde_nu!_2etter A1 g ON (sgrde_nu!/ggrde_nu!)7

INNER JOIN aci* as a CROSS JOIN

1ELECT n!e, wn!e ROM student INNER JOIN

work7

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I 4ac +ou do o eed eier

JOIN aci* as a INNER JOIN1ELECT sgrde_nu!, ggrde_2etterROM student_work A1 sJOIN grde_nu!_2etter A1 g ON (sgrde_nu!/ggrde_nu!)7

JOIN aci* as a CROSS JOIN

1ELECT n!e, wn!e ROM student JOIN work7

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JOIN c.ause

ON () or USING(:::)

Ca speci4+ i e 7HERE c.ause

Same resu.s

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8+ $es #racices

"o use a comma o oi Ue-peced eavior 1i oer JOINs i a !uer+

Never use JOIND a.1a+s use INNER JOIN orCROSS JOIN

7oever deu*s 1i.. 2o1 +our ieio

Use a JOIN c.ause isead o4 a 7HERE c.ause

8ore c.ear 1a is a 4i.er ad 1a is a oi

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Gei* e .eer *rades

sude?1or2 *rade?um?.eer

AS s AS *

sude?id *rade?um?.eer

1or2?id s:*rade?um@

*rade?um?.eer *:*rade?um

4or?*rade

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OUTER JOIN

So1 a.. ro1s a mac o oe side*e a.. *rades 4or es5

1ELECT n!e, wn!e, grde_nu!ROM student CRO11 JOIN workLET OUTER JOIN student_workU1IN. (student_id,work_id)K0ERE wn!e/Ftest3F7

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OUTER JOIN

LEFT OUTER JOIN

RIGHT OUTER JOIN

OUTER is reduda

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LEFT JOIN, ic.usive

a.e ; over.ap a.e =

;:co.; ;:co.=@ =:co.=

;:co.5 =:co.; =:co.5

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LEFT JOIN, e-c.usive

a.e ; over.ap a.e =

;:co.; ;:co.=@ =:co.=

;:co.5 =:co.; =:co.5

::::7HERE =:co.; IS NULL

RIGHT JOIN is us a mirror ima*e

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FULL OUTER JOIN

"oes o e-is i 8+S%L

Ca e simu.aed

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FULL OUTER JOIN, ic.usive

a.e ; over.ap a.e =

;:co.= ;:co.;@ =:co.=

;:co.5 =:co.; =:co.5

SELECT FRO8 .; LEFT JOIN .= :::

UNION KALL FRO8 .; RIGHT JOIN .=

UNION 1i.. e.imiae dup.icae ro1s UNION ALL us adds o*eer e = ses

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FULL OUTER JOIN

I4 i is a.read+ i e 4irs resu., do o pu i i esecod resu.

SELECT FRO8 .; LEFT JOIN .= :::

UNION ALL FRO8 .; RIGHT JOIN .=

7HERE .;:co. IS NULL

I e =d!uer+ i e uio, o.+ ro1s a ave omac i .; are a2e:

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FULL OUTER JOIN, e-c.usive

a.e ; over.ap a.e =

;:co.= ;:co.;@ =:co.=

;:co.5 =:co.; =:co.5

SELECT FRO8 .; LEFT JOIN .= :::7HERE .=:co.; IS NULL

UNION ALL SELECT FRO8 .; RIGHT JOIN .= 7HERE .;:co. IS NULL

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NATURAL modi4ier

"oes o use a JOIN c.ause JOIN c.ause is allmaci* 4ie.d ames

7or2s 4or

NATURAL JOIN

NATURAL LEFT JOIN

NATURAL RIGHT JOIN

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NATURAL JOIN e-amp.e

Isead o41ELECT n!e,grde_nu!ROM student INNER JOIN student_work U1IN.(student_id)K0ERE n!e/F1$eeri Cr2F7

7rie

1ELECT n!e,grde_nu!

ROM student NATURAL JOIN student_workK0ERE n!e/F1$eeri Cr2F7

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NATURAL JOIN *oe a1r+Havi* e same 4ie.d ames 1e e 4ie.ds are

o e!ua.1ELECT swgrde_nu!, gn2grde_2etter ROMstudent_work A1 sw INNER JOINgrde_nu!_2etter A1 gn2 U1IN. (grde_nu!)7

Is NOT e!uiva.e o

1ELECT swgrde_nu!, gn2grde_2etter ROMstudent_work A1 sw NATURAL JOINgrde_nu!_2etter A1 gn27

Tis is 1+ e 4ie.d is ca..ed 1or2:1ame

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Su!ueries

A su!uer+ is a !uer+ 1ii a !uer+8ore aura. 1a+ o4 i2i* 4or procedura.i2ers

S%L is dec.araive, ad opimiMed a 1a+

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#rocedura. Ti2i*

Ho1 o *e e ames ad *rades 4or es;

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

Ge ames ad *radesSELECT ame, *rade?um

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?umsar 1i e oi a.e

FRO8 sude?1or2

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?umFRO8 sude?1or2

*e e ame

INNER JOIN sude USING (sude?id)

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?umFRO8 sude?1or2

INNER JOIN sude USING (sude?id)

$u o.+ *e es;

7HERE 1or2?id IN (SELECT 1or2?id FRO8 1or27HERE 1ame@es;)

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?umFRO8 sude?1or2

INNER JOIN sude USING (sude?id)

7HERE 1or2?id IN (SELECT 1or2?id FRO8 1or27HERE 1ame@es;)D

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#rocedura. Ti2i* Ge e amesad *rades 4or es;

SELECT ame, *rade?umFRO8 sude?1or2

INNER JOIN sude USING (sude?id)

7HERE 1or2?id IN (SELECT 1or2?id FRO8 1or27HERE 1ame@es;)D

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"ec.araive Ti2i* Ge e amesad *rades 4or es;

I ave 5 ses o4 daasude as e ame

sude?1or2 as e *rades

1or2 as e ame o4 e assi*me

SELECT ame, *rade?um FRO8 :::: 7HERE1ame@es;

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"ec.araive Ti2i* Ge e amesad *rades 4or es;

sude ad sude?1or2 re.ae + sude?idSELECT ame, *rade?um FRO8

sude INNER JOIN sude?1or2 USING(sude?id)

::::

7HERE 1ame@es;D

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"ec.araive Ti2i* Ge e amesad *rades 4or es;

1or2 ad sude?1or2 re.ae + 1or2?idSELECT ame, *rade?um FRO8

sude INNER JOIN sude?1or2 USING(sude?id)

INNER JOIN 1or2 USING (1or2?id)

7HERE 1ame@es;D

1ELECT n!e, wn!e, grde_nu!

ROM student CRO11 JOIN workLET OUTER JOIN student_workU1IN. (student_id,work_id)K0ERE wn!e/Ftest3F7

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$u:::::

Ta 4a..s apar 4or es5, ecause Seeri did oa2e es5:

So o1 1a

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Ge a.. *rades 4or es5

Sar 1iSELECT ame, *rade?um FRO8::::

7HERE 1ame@es5D

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Ge a.. *rades 4or es5

7e 1a a .isi* 4or eac ro1 i 1or2 a*aiseac ro1 i sude

SELECT ame, *rade?um

FRO8 sude CROSS JOIN 1or2

::::

7HERE 1ame@es5D

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Ge a.. *rades 4or es5

We want a listing for each row in work againsteach row in student

7a 1e 1a, o o1 o *e i: Tas dec.araive

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Ge a.. *rades 4or es5

Grades mi* o e-is 4or a.. e ro1s:::so 1e.. eed a ouer oi

Fi.. i e va.ues 4rom sude?1or2 4or e *radesa do e-is, oii* o sude?id ad 1or2?id

SELECT ame, *rade?um

FRO8 sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame@es5D

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"rop e .o1es es score

Ho1

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"rop e .o1es es score

Ge a.. essSELECT ame, *rade?um

FRO8 sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame .i2e es?D

7e e-pec = ro1s reured::::

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"rop e .o1es es score

Ge miimum *rade 4rom a.. ess perpersoSELECT ame, mi(*rade?um)

FRO8 sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame .i2e es?

GROU# $& sude?idD

7e e-pec ro1s

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"rop e .o1es es score

Cover o a U#"ATE saeme:::::SELECT ame, mi(*rade?um)

FRO8 sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame .i2e es?

GROU# $& sude?idD

Tis is ard

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"rop e .o1es es scoreNo1 add i e res:::

U#"ATE sude?1or2 as updINNER JOIN sude?1or2 as se. USING(sude?id, 1or2?id)

RIGHT JOIN sude USING (sude?id, 1or2?id)

CROSS JOIN 1or2

SET upd:4or?*rade@ 7HERE 1ame .i2e es?

AN" upd:*rade?um@mi(se.:*rade?um)

GROU# $& se.:sude?idD

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Ta does 1or2::::Someimes +ou eed a su!uer+:::::

U#"ATE sude?1or2SET 4or?*rade@ 7HERECONCAT(sude?id,1or2?id) IN (SELECTCONCAT(sude?id,1or2?id) FRO8

sude CROSS JOIN 1or2

LEFT JOIN sude?1or2 USING (sude?id,1or2?id) 7HERE 1ame .i2e es?

GROU# $& sude?id)D

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Ta does 1or2 eier::::Someimes +ou eed o do i i ; !uer+

Someimes is o ecessar+, u more opima.#ro.em is e mi(*rade?um)::::GROU# $&

So use a emporar+ a.e

CREATE TE8#ORAR& TA$LE *rade?o?dropSELECT mi(coa.esce(*rade?um,6)) FRO8sude CROSS JOIN 1or2 LEFT JOIN sude?1or2USING (sude?id,1or2?id) 7HERE 1ame .i2e

es? *roup + sude?idD

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Temporar+ a.e

CREATE TEM+ORAR TABLE grde_to_dro (student_id tinyint unsigned not nu22,work_id tinyint unsigned de*u2t nu22,grde_nu! tinyint unsigned de*u2t nu22)7

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Temporar+ a.e

IN1ERT INTO grde_to_dro (student_id,

grde_nu!)1ELECT student_id,!in(#o2es#e(grde_nu!,;))ROM student CRO11 JOIN workLET JOIN student_work U1IN.(student_id,work_id)K0ERE wn!e 2ike Ftest_F.ROU+ B student_id7

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Temporar+ a.eU+'ATE grde_to_dro A1 gtd INNER JOINstudent_work A1 sw U1IN.

(student_id,grde_nu!)1ET gtdwork_id / swwork_id 7

U+'ATE student_work A1 sw INNER JOINgrde_to_dro A1 gtd U1IN.(student_id,work_id)1ET sw*or_grde/FnF 7

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Temporar+ a.e

Reet *or droing t$e 2owest $o!ework

'RO+ TABLE I EI1T1 grde_to_dro7

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8ore es pracices

EP#LAIN a.. +our !ueries, ad *e e es +pepossi.e

Avoid JOIN is (ide- is, STRAIGHT?JOIN)

Tr+ o opimiMe su!ueries io JOINs i4 possi.e

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Tas i

%uesios

Commes