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VLERA JAN MAR NGA DIAGRAMI I ERISIT
vlera specifike per rolin e puntorit
qe do te thot qe ka vlera bosh per profesionet e tjera
do lidhet tabela pilot me tab fluturime per te gjetur mesataren
kur behet lidhja me pilot dhe fluturime do lidhet me puntor sepse pilot eshte pjes e tab puntor
behet join
TAB puntor ka 100
tab fluturime ka 100
behen 10000 krahasime
sepse 100*100 ul performancen
entiteti supertip
do krijohet supertip
emer mbiemer dat punsimi
nen tip me 3 atribute te vecanta
__________________________________________________________________________________________
1. supertip vendosen atributet perbashkta (emer mbiemer dat punsimi)
2. nentip vendosen atributet e vecanta (dieta licensa etj)
3. ID kalon te supertipi dhe id trashgohet tek te gjith nentipet (piloti do ket pun_ID mekaniku do ket PUN_ID)
PK, FK bashke
nese eshte pk dhe fk bashk tregon trashgimi ne kete rast nuk vendoset mardhenia sepse dihet qe eshte nje me nje
4. Kufizimi
kufizimi i ndarjes dhe kufizimin i mbivendosjes
(d) ndarje - disjoint MAX 1
(o) mbivendosje - overlap MAX shume
(=) i plot
(-) i pjesshem
kombinohen psh ( ndarje e plot)
ndarje eshtenje lement e supertipit nuk mund te jet pjes e me shume se nje nentip
ndarje e plot MIN 1 (nje element i supertipit mund te lidhet me nje dhe vetem nje nentip)[1:1]
ndarje e pjesshme MIN 0 [0:1] (jo me shume se nje )
mbivendosje e plot (te pakten nje) [1:M]
mbivendsoje e pjesshme (nuk ka kufizim) [0:M]
5. Diskriminusi
eshte nje atribut te entiteti supertip i cili percakton se kujt nentipi i perket ai element
vlerat qe mer diskriminusi shenohen ne diagram (P M K )
Diskriminusi kur kemi ndarje do ket nje diskriminus te perbashket
kur kemi mbivendosje bejm shume diskriminues
praktikisht behen nga nje diskriminues per cdo nentip
pra kemi 3 nentipe 3 diskriminus
PUN_PIL 0:1
PUN_MEK 0:1
PUN_KON 0:1
PUN_TIP CHAR (1) CHECK ('P', 'M', 'K')
PUN_PIL BIT NOT NULL
SELECT * (20100 VEPRIME)
FROM PERSON P, PUNETOR PU
WHERE P.PER_ID=PU.PER_ID
AND PUN_DAT >= '01-10-2019'
__________
SELECT * (10100 VEPRIME)
FROM PERSON
WHERE PER_ID IN (SELECT PER_ID FROM PUNETOR WHERE PUN_DAT >= '01-10-2019')
__________________________________________________
CREATE VIEW AS KOT (5100 VEPRIME)
SELECT *
FROM PERSON
WHERE PER_PUN = 1;
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