Model Relasi. Eri Prasetyo. Sources :

Transkripsi

1 Model Relsi Eri Prsetyo Sources : -Dtbse Systems: Design, Implementtion & mngement, 5 th, edition, Rob & Coronel - Dtbse System Concept, Silberschtz, Korth nd Sudrshn

2 Mode Relsi Dt dn hubungn ntr dt direpresentsikn dengn kumpuln tbel yng mempunyi kolom dengn nm yng unik. Kolom merepresentsikn nm field/atribut Bris merepresentsikn rekord / tuple

3 Relsi tbel Btch no No id product Kode mode test Kode mode test Nm mode test P/S nili tegngn Motherbord test Test RAM Cek Dos boot Cek windows

4 Bsic Structure himpunn D, D,. D n relsi r sebuh subset dri D x D x x D n sebuh relsi dlh sebuh himpunn dri n-tuples (,,, n ) dimn setip i D i contoh: jik customer-nme = {Jones, Smith, Curry, Lindsy} customer-street = {Min, North, Prk} customer-city = {Hrrison, Rye, Pittsfield} mk r = { (Jones, Min, Hrrison), (Smith, North, Rye), (Curry, North, Rye), (Lindsy, Prk, Pittsfield)} dlh sebuh relsi pd customer-nme x customer-street x customer-city

5 Skem Relsi A, A,, A n re ttributes R = (A, A,, A n ) is reltion schem E.g. Customer-schem = (customer-nme, customer-street, customer-city) r(r) is reltion on the reltion schem R E.g. customer (Customer-schem)

6 Reltion Instnce The current vlues (reltion instnce) of reltion re specified by tble An element t of r is tuple, represented by row in tble customer-nme customer-street customer-city ttributes (or columns) Jones Smith Curry Lindsy Min North North Prk Hrrison Rye Rye Pittsfield tuples (or rows) customer

7 Bhs Query Bhs yng dpt dipki penggun untuk memint tu melck informsi dri sutu bsis dt Ktegori bhs Query Procedurl Penggun hrus memberikn diskripsi urutn opersi yng dilkukn pd bsis dt untuk mendptkn informsi yng diinginkn dri bsis dt non-procedurl Penggun hny bertnggung jwb mendiskripsikn krkteristik informsi yng diinginkn tnp memberikn urutn opersi

8 Aljbr Relsionl Bhs Procedurl 6 Opersi select project union set difference Crtesin product renme The opertors tke two or more reltions s inputs nd give new reltion s result.

9 Opersi Select - Opersi ini digunkn untuk memilih tribut yng memenuhi sutu predikt tertentu. - Opersi ini menggunkn notsi σ(sigm)

10 Nottion: σ p (r) Select Opertion p is clled the selection predicte Defined s: σ p (r) = {t t r nd p(t)} Where p is formul in propositionl clculus consisting of terms connected by : (nd), (or), (not) Ech term is one of: <ttribute> op <ttribute> or <constnt> where op is one of: =,, >,. <. Exmple of selection: σ brnch-nme= Perryridge (ccount)

11 Select Opertion Exmple Reltion r A B C D σ A=B ^ D > 5 (r) A B C D 7 3 0

12 Opersi Project Digunkn untuk memilih kolom tu tribut tertentu dri tbel Opersi ini dinytkn dengn notsi Π(phi)

13 Opersionl Project Nottion: A, A,, Ak (r) where A, A re ttribute nmes nd r is reltion nme. The result is defined s the reltion of k columns obtined by ersing the columns tht re not listed Duplicte rows removed from result, since reltions re sets E.g. To eliminte the brnch-nme ttribute of ccount ccount-number, blnce (ccount)

14 Project Opertion Exmple Reltion r: A B C A,C (r) A C A C =

15 Opersi crtesin product Digunkn untuk melkukn kombinsi rekord dri stu tbel dengn tbel lin. Opersi ini memungkinkn sosisi / relsi stu tbel dengn tbel linny yng sling berkitn Dinytkn dengn notsi X (kli)

16 Crtesin-Product Opertion Nottion r x s Defined s: r x s = {t q t r nd q s} Assume tht ttributes of r(r) nd s(s) re disjoint. (Tht is, R S = ). If ttributes of r(r) nd s(s) re not disjoint, then renming must be used.

17 Crtesin-Product Opertion-Exmple Reltions r, s: r x s: A B A B C D E b b b b C D E b b r s

18 Opersi union Digunkn untuk menggbungkn isi tip tribut yng sm dri tbel yng berbed Opersi ini dinytkn dengn notsi U (union)

19 Union Opertion Nottion: r s Defined s: r s = {t t r or t s} For r s to be vlid.. r, s must hve the sme rity (sme number of ttributes). The ttribute domins must be comptible (e.g., nd column of r dels with the sme type of vlues s does the nd column of s) E.g. to find ll customers with either n ccount or lon customer-nme (depositor) customer-nme (borrower)

20 Union Opertion Exmple Reltions r, s: A B A B 3 r s r s: A B 3

21 Opersi Set Difference Dinytkn dengn notsi (minus) Digunkn untuk mendptkn tuple yng berd pd stu relsi, tetpi tidk berd pd relsi yng lin

22 Set Difference Opertion Nottion r s Defined s: r s = {t t r nd t s} Set differences must be tken between comptible reltions. r nd s must hve the sme rity ttribute domins of r nd s must be comptible

23 Set Difference Opertion Exmple Reltions r, s: A B A B 3 r s r s: A B

24 Composition of Opertions Cn build expressions using multiple opertions Exmple: σ A=C (r x s) r x s A B C D E b b b b A B C D E σ A=C (r x s) b

25 Renme Opertion Allows us to nme, nd therefore to refer to, the results of reltionl-lgebr expressions. Allows us to refer to reltion by more thn one nme. Exmple: ρ x (E) returns the expression E under the nme X If reltionl-lgebr expression E hs rity n, then ρ x (A, A,, An) (E) returns the result of expression E under the nme X, nd with the ttributes renmed to A, A,., An.

26 Bnking Exmple brnch (brnch-nme, brnch-city, ssets) customer (customer-nme, customer-street, customer-only) ccount (ccount-number, brnch-nme, blnce) lon (lon-number, brnch-nme, mount) depositor (customer-nme, ccount-number) borrower (customer-nme, lon-number)

27 Bnking Exmple brnch (brnch-nme, brnch-city, ssets) customer (customer-nme, customer-street, customer-only) ccount (ccount-number, brnch-nme, blnce) lon (lon-number, brnch-nme, mount) depositor (customer-nme, ccount-number) borrower (customer-nme, lon-number)

28 Exmple Queries Find ll lons of over $00 σ mount > 00 (lon) Find the lon number for ech lon of n mount greter thn $00 lon-number (σ mount > 00 (lon))

29 Exmple Queries Find the nmes of ll customers who hve lon t the Perryridge brnch. customer-nme (σ brnch-nme= Perryridge (σ borrower.lon-number = lon.lon-number (borrower x lon))) Find the nmes of ll customers who hve lon t the Perryridge brnch but do not hve n ccount t ny brnch of the bnk. customer-nme (σ brnch-nme = Perryridge (σ borrower.lon-number = lon.lon-number (borrower x lon))) customer-nme (depositor)

30 Exmple Queries Find the nmes of ll customers who hve lon t the Perryridge brnch. Query customer-nme (σ brnch-nme = Perryridge ( σ borrower.lon-number = lon.lon-number (borrower x lon))) Query customer-nme (σ lon.lon-number = borrower.lon-number ( (σ brnch-nme = Perryridge (lon)) x borrower))

31 Exmple Queries Find the lrgest ccount blnce Renme ccount reltion s d The query is: blnce (ccount) - ccount.blnce (σ ccount.blnce < d.blnce (ccount x ρ d (ccount)))

32 Forml Definition A bsic expression in the reltionl lgebr consists of either one of the following: A reltion in the dtbse A constnt reltion Let E nd E be reltionl-lgebr expressions; the following re ll reltionl-lgebr expressions: E E E - E E x E σ p (E ), P is predicte on ttributes in E s (E ), S is list consisting of some of the ttributes in E ρ x (E ), x is the new nme for the result of E

33 Additionl Opertions We define dditionl opertions tht do not dd ny power to the reltionl lgebr, but tht simplify common queries. Set intersection Nturl join Division Assignment

34 Set-Intersection Opertion Nottion: r s Defined s: r s ={ t t r nd t s } Assume: r, s hve the sme rity ttributes of r nd s re comptible Note: r s = r - (r - s)

35 Set-Intersection Opertion - Exmple Reltion r, s: A B A B 3 r s r s A B

36 Nottion: r s Nturl-Join Opertion Let r nd s be reltions on schems R nd S respectively. Then, r s is reltion on schem R S obtined s follows: Consider ech pir of tuples t r from r nd t s from s. If t r nd t s hve the sme vlue on ech of the ttributes in R S, dd tuple t to the result, where Exmple: t hs the sme vlue s t r on r t hs the sme vlue s t s on s R = (A, B, C, D) S = (E, B, D) Result schem = (A, B, C, D, E) r s is defined s: r.a, r.b, r.c, r.d, s.e (σ r.b = s.b r.d = s.d (r x s))

37 Nturl Join Opertion Exmple Reltions r, s: A B δ 4 C D b b B 3 3 D b b E δ r A B δ C D b E δ s r s

38 Division Opertion Suited to queries tht include the phrse for ll. Let r nd s be reltions on schems R nd S respectively where R = (A,, A m, B,, B n ) S = (B,, B n ) r s The result of r s is reltion on schem R S = (A,, A m ) r s = { t t R-S (r) u s ( tu r ) }

39 Division Opertion Exmple Reltions r, s: A B B r s: A δ δ δ r s

40 Another Division Exmple A B C D b b b b E 3 Reltions r, s: r s: D b E A B C r s

41 Division Opertion (Cont.) Property Let q r s Then q is the lrgest reltion stisfying q x s r Definition in terms of the bsic lgebr opertion Let r(r) nd s(s) be reltions, nd let S R r s = R-S (r) R-S ( ( R-S (r) x s) R-S,S (r)) To see why R-S,S (r) simply reorders ttributes of r R-S ( R-S (r) x s) R-S,S (r)) gives those tuples t in R-S (r) such tht for some tuple u s, tu r.

42 Assignment Opertion The ssignment opertion ( ) provides convenient wy to express complex queries. Write query s sequentil progrm consisting of series of ssignments followed by n expression whose vlue is displyed s result of the query. Assignment must lwys be mde to temporry reltion vrible. Exmple: Write r s s temp R-S (r) temp R-S ((temp x s) R-S,S (r)) result = temp temp The result to the right of the is ssigned to the reltion vrible on the left of the. My use vrible in subsequent expressions.

43 Exmple Queries Find ll customers who hve n ccount from t lest the Downtown nd the Uptown brnches. Query CN (σ BN= Downtown (depositor ccount)) CN (σ BN= Uptown (depositor ccount)) where CN denotes customer-nme nd BN denotes brnch-nme. Query customer-nme, brnch-nme (depositor ccount) ρ temp(brnch-nme ) ({( Downtown ), ( Uptown )})

44 Exmple Queries Find ll customers who hve n ccount t ll brnches locted in Brooklyn city. customer-nme, brnch-nme (depositor ccount) brnch-nme (σ brnch-city = Brooklyn (brnch))