{"id":595,"date":"2010-08-24T13:48:00","date_gmt":"2010-08-24T05:48:00","guid":{"rendered":"http:\/\/note.systw.net\/note\/?p=595"},"modified":"2023-11-04T13:49:22","modified_gmt":"2023-11-04T05:49:22","slug":"%e8%b3%87%e6%96%99%e5%ba%aber-model","status":"publish","type":"post","link":"https:\/\/systw.net\/note\/archives\/595","title":{"rendered":"\u8cc7\u6599\u5eabER-model"},"content":{"rendered":"\n

ER-model(\u5be6\u9ad4\u95dc\u806f\u6a21\u5f0f)<\/strong>
\u4ee5\u8cc7\u6599\u70ba\u4e3b\u8981\u8003\u91cf\u65b9\u5411,\u9069\u7576\u7684\u8a2d\u8a08\u53ef\u4ee5\u89e3\u6c7a\u8cc7\u6599\u4e0d\u4e00\u81f4\u7684\u554f\u984c
\u57fa\u672c\u7d44\u6210\u70ba<\/strong>
entity(\u5be6\u9ad4)
relationship(\u95dc\u4fc2)<\/p>\n\n\n\n

\u8cc7\u6599\u6a21\u578b\u5206\u70ba
Conceptual Data Model(\u6982\u5ff5\u8cc7\u6599\u6a21\u578b)\/High Level Data Model(\u9ad8\u968e\u8cc7\u6599\u6a21\u578b)<\/strong>:\u9069\u5408\u4e00\u822c\u4f7f\u7528\u8005\u8207\u7cfb\u7d71\u5206\u6790\u5e2b\u4e4b\u9593\u6e9d\u901a
Physical Data Model(\u5be6\u9ad4\u8cc7\u6599\u6a21\u578b)\/Low Level Data Model(\u4f4e\u968e\u8cc7\u6599\u6a21\u578b)<\/strong>:\u63d0\u4f9b\u7d66\u7a0b\u5f0f\u8a2d\u8a08\u4eba\u54e1\u4f86\u5be6\u4f5c<\/p>\n\n\n\n

………………………………………………………………………………………………………………………….<\/p>\n\n\n\n

ENTITY<\/strong><\/p>\n\n\n\n

entity type\u6703\u5305\u542b
entity type name(\u5be6\u9ad4\u578b\u614b\u540d\u7a31)<\/strong>:\u901a\u5e38\u90fd\u662ftable\u540d\u7a31
entity\u7684attribute(\u5c6c\u6027)<\/strong>:\u901a\u5e38\u90fd\u662ftable\u5167\u7684\u6b04\u4f4d\u540d\u7a31
entity\u7684attribute value(\u5c6c\u6027\u503c)<\/strong>:\u901a\u5e38\u90fd\u662f\u8a72\u6b04\u4f4d\u7684\u503c
ex:\u4e00\u500b\u54e1\u5de5\u7684entity\u53ef\u80fd\u6703\u5982\u4e0b
\u54e1\u5de5(\u54e1\u5de5\u4ee3\u865f,\u59d3\u540d,\u4f4f\u5740)
\u54e1\u5de5\u662fentity type name,\u54e1\u5de5\u4ee3\u865f,\u59d3\u540d,\u4f4f\u5740\u662fattribute
ps:
Entity Type(\u5be6\u9ad4\u578b\u614b):\u5c07\u6578\u500b\u6027\u8cea\u76f8\u8fd1\u7684\u5be6\u9ad4\uff0c\u5f59\u6574\u51fa\u5171\u540c\u7684\u5c6c\u6027\u53ca\u5be6\u9ad4\u540d\u7a31<\/p>\n\n\n\n

entity type\u5206\u70ba
[strong entity(\u5f37\u5be6\u9ad4)]<\/strong>
\u5177\u6709key attribute\u7684entity
\u53ef\u7368\u7acb\u5b58\u5728
[[weak entity(\u5f31\u5be6\u9ad4)]]<\/strong>
\u4e0d\u5177\u6709key attribute\u7684entity
\u7121\u6cd5\u7368\u7acb\u5b58\u5728\u7684entity,\u9700\u4f9d\u9644\u5728\u5176\u4ed6entity\u624d\u53ef\u5b58\u5728\u7684entity<\/p>\n\n\n\n

…..<\/p>\n\n\n\n

attribute\u7684\u985e\u578b
key attribute(\u9375\u503c\u5c6c\u6027)<\/strong> \u5177\u552f\u4e00\u6027\u8cea\u7684\u6b04\u4f4d
\u3000\u552f\u4e00\u8b58\u5225\u8a72\u5be6\u9ad4\u7684\u5c6c\u6027
\u3000\u4e0d\u53ef\u6709\u91cd\u8907\u503c\u7522\u751f
\u3000\u4e0d\u53ef\u6709Null Value(\u7a7a\u503c)\u7684\u60c5\u5f62
\u3000ex:\u54e1\u5de5\u7de8\u865f
\u95dc\u4fc2\u5c6c\u6027<\/strong>
\u3000\u7528\u5728relationshiprt\u7684attribute,\u5e38\u767c\u751f\u5728\u591a\u5c0d\u591a\u95dc\u4fc2<\/p>\n\n\n\n

single attribute(\u55ae\u503c\u5c6c\u6027)<\/strong> ex:\u6027\u5225
multi attribute(\u591a\u503c\u5c6c\u6027)<\/strong> ex:\u96fb\u8a71,\u5b78\u6b77,\u7d93\u6b77<\/p>\n\n\n\n

Atomic Attribute(\u55ae\u5143\u578b\u5c6c\u6027)<\/strong> \u4e0d\u80fd\u518d\u88ab\u5207\u5272\u6210\u66f4\u5c0f\u7684\u5c6c\u6027 ex:\u7e23\u5e02
Composite Attribute(\u8907\u5408\u578b\u5c6c\u6027)<\/strong> \u53ef\u518d\u88ab\u5207\u5272\u6210\u66f4\u5c0f\u4e0d\u540c\u5c6c\u6027\u7684\u7d44\u5408
ex:\u5730\u5740,\u56e0\u70ba\u53ef\u4ee5\u5728\u88ab\u5207\u6210\u7e23\u5e02,\u5340,\u8def,…\u7b49<\/p>\n\n\n\n

Stored Attribute(\u5132\u5b58\u578b\u5c6c\u6027)<\/strong> ex:\u751f\u65e5
Derived Attribute(\u884d\u751f\u578b\u5c6c\u6027)<\/strong> \u53ef\u5f9e\u5176\u4ed6\u5c6c\u6027\u503c\u63a8\u7b97\u51fa\u4f86
ex:\u5e74\u9f61,\u53ef\u7531\u751f\u65e5\u8207\u76ee\u524d\u6642\u9593\u63a8\u7b97\u51fa\u4f86<\/p>\n\n\n\n

………………………………………………………………………………………………………………………….<\/p>\n\n\n\n

RELATIONSHIP<\/strong><\/p>\n\n\n\n

relationship\u4f9dconnectivity\u6709\u4ee5\u4e0b\u5e7e\u7a2e
1  < R> 1 (\u4e00\u5c0d\u4e00\u95dc\u4fc2)
1 < R> n \/ m < R> 1 (\u4e00\u5c0d\u591a\u95dc\u4fc2\/\u591a\u5c0d\u4e00\u95dc\u4fc2)
m < R> <\/strong>n (\u591a\u5c0d\u591a\u95dc\u4fc2)<\/strong>
ex:
\u4e00\u500b\u5b78\u751f\u53ef\u4ee5\u9078\u4fee\u591a\u500b\u8ab2\u7a0b,\u4e00\u500b\u8ab2\u7a0b\u53ef\u4ee5\u88ab\u5f88\u591a\u5b78\u751f\u4fee
[\u5b78\u751f]—–M<\u9078\u4fee>N—–[\u8ab2\u7a0b]<\/p>\n\n\n\n

R(relationship)\u53ef\u5206
< weak R(\u5f31\u95dc\u4fc2)><\/strong>
[\u5f37\u5be6\u9ad4] <\u5f31R> [\u5f37\u5be6\u9ad4]
ps:\u5f37\u5be6\u9ad4\u7684PK\u4e0d\u6703\u4e5f\u662fFK
< < strong R(\u5f37\u95dc\u4fc2)>>
<\/strong>[\u5f37\u5be6\u9ad4] <<\u5f37R\/\u8b58\u5225R>> [[\u5f31\u5be6\u9ad4]]
ps:\u5be6\u9ad4\u7684PK\u82e5\u4e5f\u662fFK,\u5247\u70ba\u5f31\u5be6\u9ad4<\/p>\n\n\n\n

\u53c3\u8207\u95dc\u4fc2:
\u90e8\u4efd\u53c3\u8207<\/strong>,\u8a72\u5be6\u9ad4\u7684\u9375\u503c\u5c6c\u6027\u4e26\u4e0d\u662f\u6bcf\u4e00\u500b\u90fd\u6703\u5c0d\u61c9\u5230\u53e6\u4e00\u500b\u5be6\u9ad4\u7684\u9375\u503c\u5c6c\u6027
peter chain\u8868\u793a\u6cd5\u75281\u689d\u7dda\u8868\u793a
\u5168\u90e8\u53c3\u8207<\/strong>,\u8a72\u5be6\u9ad4\u9375\u503c\u5c6c\u6027\u6703\u5b8c\u5168\u5c0d\u61c9\u5230\u53e6\u4e00\u500b\u5be6\u9ad4\u7684\u9375\u503c\u5c6c\u6027
peter chain\u8868\u793a\u6cd5\u75282\u689d\u7dda\u8868\u793a
<\/strong>ex:
[\u5b78\u751f]—===[\u76e3\u8b77\u4eba]
\u5b78\u751f\u90e8\u4efd\u53c3\u8207\u76e3\u8b77\u4eba ,\u56e0\u70ba\u4e26\u975e\u6240\u6709\u5b78\u751f\u90fd\u6709\u76e3\u8b77\u4eba
\u76e3\u8b77\u4eba\u5168\u90e8\u53c3\u8207\u5b78\u751f ,\u53ea\u8981\u6709\u76e3\u8b77\u4eba\u4e00\u5b9a\u6703\u5c0d\u61c9\u5230\u5b78\u751f<\/p>\n\n\n\n

cardinality(\u57fa\u6578)
<\/strong>\u53c3\u8207\u6578\u7684\u9650\u5236
[Entity]–{min,max}–< R>–{min,max}–[Entity]
min\u4ee3\u8868\u53c3\u8207\u6578,\u82e5\u662f\u90e8\u4efd\u53c3\u8207\u5247\u70ba0,\u5168\u90e8\u53c3\u6578\u5247\u70ba1
ex:\u4ee5peter chain\u70ba\u4f8b
[\u5b78\u751f]-{1,4}–{5,30}-[\u8ab2\u7a0b]
\u5b78\u751f \u6700\u5c111\u8ab2\u7a0b,\u6700\u591a4\u8ab2\u7a0b
\u8ab2\u7a0b \u6700\u5c115\u5b78\u751f,\u6700\u591a30\u5b78\u751f<\/p>\n\n\n\n


<\/strong>………………………………………………………………………………………………………………………….<\/p>\n\n\n\n

[entity1]—< R>===[entity2]
eq
[entity1]–{0<\/strong>,x}–< R>=={1<\/strong>,y}==[entity2]
\u90e8\u4efd\u53c3\u8207\u5247min\u662f0,\u5168\u90e8\u53c3\u8207\u5247min\u662f1
eq
[entity1]–{0,x<\/strong>}–y<\/strong>< R>x<\/strong>=={1,y<\/strong>}==[entity2]
\u5728peter chain,\u672c\u5730entity\u7684max\u4ee3\u8868\u5c0d\u65b9entity\u7684connectivity
\u82e5entity1\u7684max\u70ba1\u5247\u8a72entity\u53ea\u5c0d\u61c91\u500b\u5230entity2
\u82e5entity1\u7684max\u70ban\u5247\u8a72entity\u53ef\u5c0d\u61c9n\u500b\u5230entity2
ex:
\u4ee5\u4e0b\u4ee5peter chain\u8868\u793a\u6cd5\u70ba\u4f8b
\u4e00\u500b\u5b78\u751f\u4e0d\u4e00\u5b9a\u8981\u6709\u76e3\u8b77\u4eba,\u4f46\u53ea\u80fd\u6709\u4e00\u4f4d\u76e3\u8b77\u4eba,\u800c\u4e00\u4f4d\u76e3\u8b77\u4eba\u53ef\u76e3\u8b77\u591a\u4f4d\u5b78\u751f
[\u5b78\u751f]—===[\u76e3\u8b77\u4eba] eq
[\u5b78\u751f]–{0<\/strong>,1}–< R>=={1<\/strong>,n}==[\u76e3\u8b77\u4eba] eq
[\u5b78\u751f]–{0,1<\/strong>}–n<\/strong>< R>1<\/strong>=={1,n<\/strong>}==[\u76e3\u8b77\u4eba]
\u4e00\u500b\u5b78\u751f\u4e0d\u4e00\u5b9a\u8981\u6709\u76e3\u8b77\u4eba,\u4f46\u53ef\u540c\u6642\u6709\u591a\u4f4d\u76e3\u8b77\u4eba,\u800c\u4e00\u4f4d\u76e3\u8b77\u4eba\u53ea\u53ef\u76e3\u8b77\u4e00\u4f4d\u5b78\u751f
[\u5b78\u751f]—< R>===[\u76e3\u8b77\u4eba] eq
[\u5b78\u751f]–{0,n}–< R>=={1,1}==[\u76e3\u8b77\u4eba] eq
[\u5b78\u751f]–{0,n}–1< R>n=={1,1}==[\u76e3\u8b77\u4eba]
ex:
\u6bcf\u4e00\u500b\u79d1\u7cfb\u50c5\u6703\u6709\u4e00\u500b\u5b78\u751f\u4ee3\u8868\uff0c\u53c3\u8207\u8a72\u79d1\u7cfb\u7684\u79d1\u7cfb\u6703\u8b70\uff0c\u4e26\u4e14\u4e0d\u9700\u8981\u5c07\u6b77\u5e74\u7684\u5b78\u751f\u4ee3\u8868\u8a18\u9304\uff0c\u53ea\u8981\u8a18\u9304\u76ee\u524d\u7684\u5b78\u751f\u4ee3\u8868\u5373\u53ef
\u63db\u53e5\u8a71\u8aaa\uff0c\u5b78\u751f\u53ea\u80fd\u4ee3\u8868\u4e00\u500b\u79d1\u7cfb,\u4e00\u500b\u79d1\u7cfb\u53ea\u80fd\u8b93\u4e00\u500b\u5b78\u751f\u7576\u4ee3\u8868
[\u5b78\u751f]–{0,1}–1<\u4ee3\u8868>1=={1,1}==[\u79d1\u7cfb]
ex:
\u6bcf\u4e00\u9580\u8ab2\u7a0b\u5fc5\u9808\u9650\u5236\u5b78\u751f\u7684\u4fee\u8ab2\u4eba\u6578\uff0c\u6700\u5c11\u5fc5\u9808\u9054\u5230\u4e94\u4eba\uff0c\u6700\u9ad8\u4e0d\u5f97\u9ad8\u65bc\u4e94\u5341\u4eba\u9078\u4fee\u8a72\u8ab2\u7a0b,\u800c\u5b78\u751f\u4e0d\u4e00\u5b9a\u6bcf\u500b\u90fd\u8981\u4fee\u8ab2
\u63db\u53e5\u8a71\u8aaa\uff0c\u5b78\u751f\u53ef\u4ee5\u4fee\u591a\u500b\u8ab2\u7a0b,\u4e00\u500b\u8ab2\u7a0b\u53ef\u4ee5\u88ab\u5f88\u591a\u5b78\u751f\u4fee
[\u5b78\u751f]–{0,n}–m<\u9078\u4fee>n=={5,50}==[\u8ab2\u7a0b]<\/p>\n\n\n\n

……………………<\/p>\n\n\n\n

\u722a\u5716\u8868\u793a\u6cd5
{0,n} = \u5716\u793a o< \u6216 >o
{0,1} = \u5716\u793a o| \u6216 |o
{1,1} = \u5716\u793a | |
{1,n} = \u5716\u793a |<
ps:
{x,y}\u610f\u7fa9\u5982\u4e0b
y=peter chain\u7684connectivities
x\u8868\u793a\u53c3\u8207\u95dc\u4fc2,\u82e5\u70ba| \u8868\u793a\u90e8\u4efd\u53c3\u6578,\u82e5\u70bao\u8868\u793a\u5168\u90e8\u53c3\u8207<\/p>\n\n\n\n

\u722a\u5716\u8868\u793a\u6cd5\u548cpeter chain\u8868\u793a\u6cd5\u6bd4\u8f03
[E1]o| {0,1} ——– {1,1} | | [E2] = [E1]—{1,1}—1< R>1—{0,1}—[E2]
[E1]o| {0,1} ——– {1,N} |< [E2] = [E1]—{1,N}—1< R>N—{0,1}—[E2]<\/p>\n","protected":false},"excerpt":{"rendered":"

ER-model(\u5be6\u9ad4\u95dc\u806f\u6a21\u5f0f)\u4ee5\u8cc7\u6599\u70ba\u4e3b\u8981\u8003\u91cf\u65b9\u5411,\u9069\u7576\u7684 …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"fifu_image_url":"","fifu_image_alt":"","_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[16],"tags":[],"class_list":["post-595","post","type-post","status-publish","format-standard","hentry","category-database"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/posts\/595","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/comments?post=595"}],"version-history":[{"count":0,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/posts\/595\/revisions"}],"wp:attachment":[{"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/media?parent=595"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/categories?post=595"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/systw.net\/note\/wp-json\/wp\/v2\/tags?post=595"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}