{"id":13749,"date":"2023-10-25T14:09:59","date_gmt":"2023-10-25T14:09:59","guid":{"rendered":"https:\/\/tech-lib.eu\/tech\/?p=13749"},"modified":"2023-10-25T14:09:59","modified_gmt":"2023-10-25T14:09:59","slug":"pocet-primarnich-klicu-v-tabulce-zkoumani-moznosti","status":"publish","type":"post","link":"https:\/\/tech-lib.eu\/tech\/pocet-primarnich-klicu-v-tabulce-zkoumani-moznosti\/","title":{"rendered":"Po\u010det prim\u00e1rn\u00edch kl\u00ed\u010d\u016f v tabulce. Zkoum\u00e1n\u00ed mo\u017enost\u00ed"},"content":{"rendered":"
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Kolik tabulek m\u016f\u017ee m\u00edt datab\u00e1ze?<\/div>\n
Po\u010d\u00edta\u010dov\u00e1 datab\u00e1ze je kontejner objekt\u016f. Jedna datab\u00e1ze m\u016f\u017ee obsahovat v\u00edce ne\u017e jednu tabulku. Nap\u0159\u00edklad syst\u00e9m sledov\u00e1n\u00ed skladov\u00fdch z\u00e1sob, kter\u00fd vyu\u017e\u00edv\u00e1 t\u0159i tabulky, nejsou t\u0159i datab\u00e1ze, ale jedna datab\u00e1ze, kter\u00e1 obsahuje t\u0159i tabulky.<\/div>\n
\n\t\t\t\t\t Dal\u0161\u00ed informace najdete na<\/span> support.microsoft.com<\/a>\n\t\t\t\t<\/div>\n<\/p><\/div>\n
P\u0159edstavte se: V rela\u010dn\u00edch datab\u00e1z\u00edch jsou prim\u00e1rn\u00ed kl\u00ed\u010de nezbytn\u00e9, proto\u017ee funguj\u00ed jako odli\u0161n\u00e9 identifik\u00e1tory pro ka\u017ed\u00fd z\u00e1znam v tabulce. Podporuj\u00ed efektivn\u00ed vyhled\u00e1v\u00e1n\u00ed dat a pom\u00e1haj\u00ed zajistit jejich integritu. \u010casto v\u0161ak nen\u00ed jasn\u00e9, kolik prim\u00e1rn\u00edch kl\u00ed\u010d\u016f m\u016f\u017ee tabulka obsahovat. Tento \u010dl\u00e1nek prozkoum\u00e1 n\u011bkolik okolnost\u00ed a poskytne odpov\u011bdi na n\u011bkter\u00e9 \u010dasto kladen\u00e9 ot\u00e1zky t\u00fdkaj\u00edc\u00ed se prim\u00e1rn\u00edch kl\u00ed\u010d\u016f v r\u016fzn\u00fdch datab\u00e1zov\u00fdch architektur\u00e1ch. Kolik hlavn\u00edch kl\u00ed\u010d\u016f m\u016f\u017ee b\u00fdt v tabulce? <\/p>\n
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Tabulka m\u016f\u017ee m\u00edt obvykle pouze jeden prim\u00e1rn\u00ed kl\u00ed\u010d. Ka\u017ed\u00fd z\u00e1znam v tabulce by m\u011bl m\u00edt prim\u00e1rn\u00ed kl\u00ed\u010d, kter\u00fd jej jednozna\u010dn\u011b identifikuje, co\u017e usnad\u0148uje na\u010d\u00edt\u00e1n\u00ed dat a zabra\u0148uje duplicitn\u00edm nebo nulov\u00fdm z\u00e1znam\u016fm. Prim\u00e1rn\u00ed kl\u00ed\u010de chr\u00e1n\u00ed integritu dat vynucen\u00edm t\u00e9to jedine\u010dnosti a umo\u017e\u0148uj\u00ed efektivn\u00ed dotazov\u00e1n\u00ed. Kolik hlavn\u00edch kl\u00ed\u010d\u016f je v tabulce SAP povoleno? Stejn\u00e1 z\u00e1kladn\u00ed my\u0161lenka je z\u00e1kladem v\u0161ech datab\u00e1zov\u00fdch syst\u00e9m\u016f, v\u010detn\u011b spole\u010dnosti SAP, zn\u00e1m\u00e9ho poskytovatele softwaru pro pl\u00e1nov\u00e1n\u00ed podnikov\u00fdch zdroj\u016f. Tabulka v syst\u00e9mu SAP sm\u00ed m\u00edt tak\u00e9 pouze jeden prim\u00e1rn\u00ed kl\u00ed\u010d. D\u00edky tomu je umo\u017en\u011bna bezprobl\u00e9mov\u00e1 integrace a sd\u00edlen\u00ed dat, stejn\u011b jako konzistence a kompatibilita s jin\u00fdmi datab\u00e1zov\u00fdmi syst\u00e9my. Prim\u00e1rn\u00ed kl\u00ed\u010d je obvykle omezen na jeden v ka\u017ed\u00e9 tabulce, proto ano, v ka\u017ed\u00e9 tabulce m\u016f\u017ee b\u00fdt pouze jeden prim\u00e1rn\u00ed kl\u00ed\u010d. Je d\u016fle\u017eit\u00e9 si uv\u011bdomit, \u017ee prim\u00e1rn\u00ed kl\u00ed\u010d m\u016f\u017ee obsahovat mnoho sloupc\u016f. Slo\u017een\u00fd prim\u00e1rn\u00ed kl\u00ed\u010d je takov\u00fd kl\u00ed\u010d, ve kter\u00e9m je zkombinov\u00e1no n\u011bkolik sloupc\u016f, aby byl vytvo\u0159en jedin\u00fd, odli\u0161n\u00fd identifik\u00e1tor pro ka\u017ed\u00fd z\u00e1znam v datab\u00e1zi. Za takov\u00fdch okolnost\u00ed mus\u00ed b\u00fdt kombinace t\u011bchto sloupc\u016f odli\u0161n\u00e1, ale hodnoty jednotliv\u00fdch sloupc\u016f jsou p\u0159\u00edpustn\u00e9. <\/p>\n

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Kolik prim\u00e1rn\u00edch kl\u00ed\u010d\u016f m\u016f\u017ee m\u00edt tabulka SQL? Tabulka v jazyce SQL (Structured Query Language) m\u016f\u017ee m\u00edt nav\u00edc pouze jeden prim\u00e1rn\u00ed kl\u00ed\u010d. Podobn\u011b jako v jin\u00fdch datab\u00e1zov\u00fdch syst\u00e9mech se v jazyce SQL dodr\u017euje integrita a jedine\u010dnost pomoc\u00ed jedin\u00e9ho prim\u00e1rn\u00edho kl\u00ed\u010de. Slo\u017een\u00e9 prim\u00e1rn\u00ed kl\u00ed\u010de, v nich\u017e je spojeno v\u00edce sloupc\u016f, aby se vytvo\u0159il jedin\u00fd jedine\u010dn\u00fd identifik\u00e1tor, jsou nicm\u00e9n\u011b v SQL podporov\u00e1ny. Vy\u017eaduje ka\u017ed\u00e1 tabulka prim\u00e1rn\u00ed kl\u00ed\u010d? <\/p>\n

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I kdy\u017e prim\u00e1rn\u00ed kl\u00ed\u010d nen\u00ed nutn\u011b vy\u017eadov\u00e1n pro ka\u017edou tabulku, d\u016frazn\u011b se doporu\u010duje a pova\u017euje se za osv\u011bd\u010den\u00fd postup. Prim\u00e1rn\u00ed kl\u00ed\u010d zaru\u010duje integritu dat, usnad\u0148uje rychl\u00e9 vyhled\u00e1v\u00e1n\u00ed dat a pom\u00e1h\u00e1 zachovat obecnou konzistenci a strukturu datab\u00e1ze. Bez prim\u00e1rn\u00edho kl\u00ed\u010de je obt\u00ed\u017en\u00e9 identifikovat a zpracov\u00e1vat z\u00e1znamy v datab\u00e1zi jedine\u010dn\u00fdm zp\u016fsobem, co\u017e m\u016f\u017ee v\u00e9st k nekonzistentn\u00edm dat\u016fm a probl\u00e9m\u016fm s v\u00fdkonem. <\/p>\n

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Shrnut\u00ed: <\/p>\n

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Z\u00e1v\u011brem lze \u0159\u00edci, \u017ee v\u011bt\u0161ina datab\u00e1zov\u00fdch syst\u00e9m\u016f, v\u010detn\u011b syst\u00e9m\u016f SAP a SQL, umo\u017e\u0148uje, aby tabulka m\u011bla pouze jeden prim\u00e1rn\u00ed kl\u00ed\u010d. I kdy\u017e m\u016f\u017ee b\u00fdt hlavn\u00ed kl\u00ed\u010d tvo\u0159en pouze jedn\u00edm sloupcem, m\u016f\u017ee to b\u00fdt tak\u00e9 slo\u017een\u00fd kl\u00ed\u010d slo\u017een\u00fd z n\u011bkolika sloupc\u016f. A\u010dkoli to nen\u00ed nutn\u00e9, je existence prim\u00e1rn\u00edho kl\u00ed\u010de nezbytn\u00e1 pro zachov\u00e1n\u00ed integrity dat a umo\u017en\u011bn\u00ed efektivn\u00edho vyhled\u00e1v\u00e1n\u00ed dat. V\u00fdvoj\u00e1\u0159i datab\u00e1z\u00ed mohou d\u00edky znalosti z\u00e1klad\u016f prim\u00e1rn\u00edch kl\u00ed\u010d\u016f vytv\u00e1\u0159et spolehliv\u00e9 a efektivn\u00ed datab\u00e1ze, kter\u00e9 spl\u0148uj\u00ed jejich jedine\u010dn\u00e9 po\u017eadavky.<\/p><\/div>\n

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FAQ<\/div>\n
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Mohou b\u00fdt v tabulce dva nebo v\u00edce prim\u00e1rn\u00edch kl\u00ed\u010d\u016f?<\/div>\n

Tabulka skute\u010dn\u011b m\u016f\u017ee obsahovat n\u011bkolik prim\u00e1rn\u00edch kl\u00ed\u010d\u016f. T\u00e9to my\u0161lence se \u0159\u00edk\u00e1 slo\u017een\u00fd prim\u00e1rn\u00ed kl\u00ed\u010d. Dva nebo v\u00edce sloupc\u016f, kter\u00e9 spole\u010dn\u011b jednozna\u010dn\u011b identifikuj\u00ed ka\u017ed\u00fd \u0159\u00e1dek v datab\u00e1zi, tvo\u0159\u00ed slo\u017een\u00fd prim\u00e1rn\u00ed kl\u00ed\u010d. \u010casto se pou\u017e\u00edv\u00e1 v p\u0159\u00edpadech, kdy sm\u011bs sloupc\u016f m\u016f\u017ee jednozna\u010dn\u011b identifikovat ka\u017ed\u00fd z\u00e1znam, ale jedin\u00fd sloupec nikoli. Pokud je jedine\u010dnost z\u00e1znamu d\u00e1na n\u011bkolika r\u016fzn\u00fdmi vlastnostmi nebo charakteristikami, m\u016f\u017ee b\u00fdt u\u017eite\u010dn\u00e9 m\u00edt v\u00edce prim\u00e1rn\u00edch kl\u00ed\u010d\u016f. <\/p>\n<\/div>\n

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M\u016f\u017ee b\u00fdt prim\u00e1rn\u00ed kl\u00ed\u010d ve v\u00edce tabulk\u00e1ch?<\/div>\n

Prim\u00e1rn\u00ed kl\u00ed\u010d se nem\u016f\u017ee vyskytovat ve v\u00edce ne\u017e jedn\u00e9 tabulce. Prim\u00e1rn\u00ed kl\u00ed\u010d v n\u00e1vrhu datab\u00e1ze je speci\u00e1ln\u00ed k\u00f3d p\u0159id\u011blen\u00fd ur\u010dit\u00e9 tabulce, aby se zajistilo, \u017ee ka\u017ed\u00fd \u0159\u00e1dek bude m\u00edt odli\u0161nou identifikaci. Pou\u017e\u00edv\u00e1 se k zachov\u00e1n\u00ed integrity dat v tabulce a k vynucen\u00ed integrity entit. Prim\u00e1rn\u00ed kl\u00ed\u010de nelze sd\u00edlet ani replikovat mezi v\u00edce tabulkami; lze je v\u0161ak pou\u017e\u00edt jako ciz\u00ed kl\u00ed\u010de v jin\u00fdch datab\u00e1z\u00edch pro vytvo\u0159en\u00ed asociac\u00ed. Aby bylo mo\u017en\u00e9 jednozna\u010dn\u011b identifikovat ka\u017ed\u00fd \u0159\u00e1dek v tabulce, m\u011bla by m\u00edt tato tabulka vlastn\u00ed sloupec nebo sloupce prim\u00e1rn\u00edho kl\u00ed\u010de. <\/p>\n<\/div>\n

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Maj\u00ed v\u0161echny tabulky prim\u00e1rn\u00ed kl\u00ed\u010d?<\/div>\n

Ne ka\u017ed\u00e1 tabulka v\u0161ak m\u00e1 prim\u00e1rn\u00ed kl\u00ed\u010d. A\u010dkoli se obvykle doporu\u010duje m\u00edt v tabulce prim\u00e1rn\u00ed kl\u00ed\u010d, zejm\u00e9na u rela\u010dn\u00edch datab\u00e1z\u00ed, existuj\u00ed situace, kdy nemus\u00ed b\u00fdt prim\u00e1rn\u00ed kl\u00ed\u010d nezbytn\u00fd nebo praktick\u00fd. Prim\u00e1rn\u00ed kl\u00ed\u010d nemus\u00ed b\u00fdt nutn\u00fd nap\u0159\u00edklad v n\u011bkter\u00fdch odkl\u00e1dac\u00edch nebo do\u010dasn\u00fdch tabulk\u00e1ch pou\u017e\u00edvan\u00fdch pro zpracov\u00e1n\u00ed dat nebo mezi v\u00fdpo\u010dty. Krom\u011b toho n\u011bkter\u00e9 datab\u00e1ze NoSQL nebo nerela\u010dn\u00ed datab\u00e1ze nemus\u00ed vy\u017eadovat pou\u017eit\u00ed prim\u00e1rn\u00edch kl\u00ed\u010d\u016f. Volba, zda v tabulce pou\u017e\u00edt prim\u00e1rn\u00ed kl\u00ed\u010d, nakonec z\u00e1vis\u00ed na po\u017eadavc\u00edch a uspo\u0159\u00e1d\u00e1n\u00ed konkr\u00e9tn\u00edho pou\u017e\u00edvan\u00e9ho datab\u00e1zov\u00e9ho syst\u00e9mu. <\/p>\n<\/div>\n

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M\u016f\u017eete m\u00edt v tabulce t\u0159i prim\u00e1rn\u00ed kl\u00ed\u010de?<\/div>\n

Odpov\u011b\u010f zn\u00ed ne, tabulka nem\u016f\u017ee m\u00edt t\u0159i hlavn\u00ed kl\u00ed\u010de. Prim\u00e1rn\u00ed kl\u00ed\u010d v rela\u010dn\u00ed datab\u00e1zi je \u010d\u00edslo, kter\u00e9 jednozna\u010dn\u011b identifikuje ka\u017ed\u00fd z\u00e1znam v tabulce. Pom\u00e1h\u00e1 udr\u017eovat integritu dat a zaji\u0161\u0165uje, \u017ee ka\u017ed\u00fd z\u00e1znam v datab\u00e1zi je jednozna\u010dn\u011b rozpoznateln\u00fd. Prim\u00e1rn\u00ed kl\u00ed\u010d nem\u016f\u017ee m\u00edt v\u00edce ne\u017e jeden prim\u00e1rn\u00ed kl\u00ed\u010d a podle definice m\u016f\u017ee b\u00fdt tvo\u0159en pouze jedn\u00edm nebo v\u00edce sloupci. <\/p>\n<\/div>\n

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Mohou dv\u011b tabulky sd\u00edlet prim\u00e1rn\u00ed kl\u00ed\u010d?<\/div>\n

Ano, existuj\u00ed p\u0159\u00edpady, kdy dv\u011b tabulky mohou sd\u00edlet prim\u00e1rn\u00ed kl\u00ed\u010d. K popisu se pou\u017e\u00edvaj\u00ed term\u00edny vztah jeden k jednomu nebo vztah sd\u00edlen\u00e9ho prim\u00e1rn\u00edho kl\u00ed\u010de. Sd\u00edlen\u00fd prim\u00e1rn\u00ed kl\u00ed\u010d se pou\u017e\u00edv\u00e1 k propojen\u00ed dvou tabulek v tomto typu vztahu tak, aby ka\u017ed\u00fd z\u00e1znam v jedn\u00e9 tabulce p\u0159esn\u011b odpov\u00eddal z\u00e1znamu v druh\u00e9 tabulce. <\/p>\n

<\/div>\n

Pokud je t\u0159eba data z logick\u00fdch nebo v\u00fdkonnostn\u00edch d\u016fvod\u016f rozd\u011blit do mnoha tabulek a z\u00e1rove\u0148 mezi nimi zachovat pevn\u00fd vztah, m\u016f\u017ee b\u00fdt tento zp\u016fsob u\u017eite\u010dn\u00fd. Vztahy se sd\u00edlen\u00fdm prim\u00e1rn\u00edm kl\u00ed\u010dem jsou m\u00e9n\u011b \u010dast\u00e9 ne\u017e vztahy typu one-to-many, kdy je prim\u00e1rn\u00ed kl\u00ed\u010d jedn\u00e9 tabulky pou\u017eit jako ciz\u00ed kl\u00ed\u010d v jin\u00e9 tabulce.<\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Kolik tabulek m\u016f\u017ee m\u00edt datab\u00e1ze? Po\u010d\u00edta\u010dov\u00e1 datab\u00e1ze je kontejner objekt\u016f. Jedna datab\u00e1ze m\u016f\u017ee obsahovat v\u00edce ne\u017e jednu tabulku. Nap\u0159\u00edklad syst\u00e9m sledov\u00e1n\u00ed skladov\u00fdch z\u00e1sob, kter\u00fd vyu\u017e\u00edv\u00e1 t\u0159i tabulky, nejsou t\u0159i datab\u00e1ze, ale jedna datab\u00e1ze, kter\u00e1 obsahuje t\u0159i tabulky. Dal\u0161\u00ed informace najdete na support.microsoft.com P\u0159edstavte se: V rela\u010dn\u00edch datab\u00e1z\u00edch jsou prim\u00e1rn\u00ed kl\u00ed\u010de nezbytn\u00e9, proto\u017ee funguj\u00ed jako odli\u0161n\u00e9 … \u010c\u00edst d\u00e1l<\/a><\/p>\n","protected":false},"author":3220,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5176],"tags":[],"class_list":["post-13749","post","type-post","status-publish","format-standard","hentry","category-database-management"],"_links":{"self":[{"href":"https:\/\/tech-lib.eu\/tech\/wp-json\/wp\/v2\/posts\/13749","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tech-lib.eu\/tech\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tech-lib.eu\/tech\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tech-lib.eu\/tech\/wp-json\/wp\/v2\/users\/3220"}],"replies":[{"embeddable":true,"href":"https:\/\/tech-lib.eu\/tech\/wp-json\/wp\/v2\/comments?post=13749"}],"version-history":[{"count":0,"href":"https:\/\/tech-lib.eu\/tech\/wp-json\/wp\/v2\/posts\/13749\/revisions"}],"wp:attachment":[{"href":"https:\/\/tech-lib.eu\/tech\/wp-json\/wp\/v2\/media?parent=13749"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tech-lib.eu\/tech\/wp-json\/wp\/v2\/categories?post=13749"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tech-lib.eu\/tech\/wp-json\/wp\/v2\/tags?post=13749"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}