[{"data":1,"prerenderedAt":1575},["ShallowReactive",2],{"note:cs\u002Fdb\u002F100+70\u002FDay10-数据库70题-综合37-47":3},{"id":4,"title":5,"body":6,"description":16,"extension":1568,"meta":1569,"navigation":1570,"path":1571,"seo":1572,"stem":1573,"__hash__":1574},"notes\u002Fsource\u002Fcs\u002Fdb\u002F100+70\u002FDay10-数据库70题-综合37-47.md","Day 10 - 数据库70题：综合题 37-47",{"type":7,"value":8,"toc":1521},"minimark",[9,13,17,22,25,38,41,52,61,64,95,104,106,128,137,139,150,158,160,166,176,179,195,210,217,219,248,253,264,269,291,305,313,315,338,358,367,369,402,405,422,438,450,458,460,493,501,523,526,541,545,547,564,570,574,577,597,600,611,615,617,634,648,656,659,779,781,812,815,832,835,839,842,903,905,908,911,987,990,1007,1010,1018,1020,1076,1078,1102,1105,1107,1119,1125,1133,1135,1232,1234,1240,1252,1256,1262,1265,1277,1280,1288,1290,1401,1422,1424,1462,1465,1476,1479,1491,1494,1510],[10,11,5],"h1",{"id":12},"day-10-数据库70题综合题-37-47",[14,15,16],"p",{},"参考重点：教材第 6 章关系数据理论。原文件中综合题 34-36 缺失，保留源文件跳号。",[18,19,21],"h2",{"id":20},"_37-指出下列关系模式是第几范式并说明理由","37. 指出下列关系模式是第几范式，并说明理由。",[14,23,24],{},"默认所有关系都已满足 1NF，即属性值不可再分。",[26,27,29,30,34,35],"h3",{"id":28},"_371-rx-y-zfxy-z","37.1 ",[31,32,33],"code",{},"R(X, Y, Z)","，",[31,36,37],{},"F={XY -> Z}",[14,39,40],{},"答案：BCNF。",[14,42,43,44,47,48,51],{},"讲解：候选码为 ",[31,45,46],{},"XY","。唯一非平凡依赖 ",[31,49,50],{},"XY -> Z"," 的左部是超码，所以满足 BCNF。",[26,53,55,56,34,58],{"id":54},"_372-rx-y-zfy-z-xz-y","37.2 ",[31,57,33],{},[31,59,60],{},"F={Y -> Z, XZ -> Y}",[14,62,63],{},"答案：3NF，但不满足 BCNF。",[14,65,66,67,69,70,73,74,77,78,77,81,84,85,88,89,91,92,94],{},"讲解：候选码有 ",[31,68,46],{}," 和 ",[31,71,72],{},"XZ","，所以 ",[31,75,76],{},"X","、",[31,79,80],{},"Y",[31,82,83],{},"Z"," 都是主属性。依赖 ",[31,86,87],{},"Y -> Z"," 中 ",[31,90,80],{}," 不是超码，违反 BCNF；但右部 ",[31,93,83],{}," 是主属性，所以满足 3NF。",[26,96,98,99,34,101],{"id":97},"_373-rx-y-zfx-y-y-x-x-yz","37.3 ",[31,100,33],{},[31,102,103],{},"F={X -> Y, Y -> X, X -> YZ}",[14,105,40],{},[14,107,108,109,73,112,114,115,118,119,73,122,34,125,127],{},"讲解：",[31,110,111],{},"X+ = XYZ",[31,113,76],{}," 是候选码；",[31,116,117],{},"Y -> X"," 且 ",[31,120,121],{},"X -> YZ",[31,123,124],{},"Y+ = XYZ",[31,126,80],{}," 也是候选码。非平凡依赖左部都是超码，因此满足 BCNF。",[26,129,131,132,34,134],{"id":130},"_374-rx-y-zfx-y-x-z","37.4 ",[31,133,33],{},[31,135,136],{},"F={X -> Y, X -> Z}",[14,138,40],{},[14,140,108,141,143,144,146,147,149],{},[31,142,111],{},"，候选码为 ",[31,145,76],{},"。所有非平凡依赖左部都是候选码 ",[31,148,76],{},"，满足 BCNF。",[26,151,153,154,34,156],{"id":152},"_375-rx-y-zfxy-z","37.5 ",[31,155,33],{},[31,157,37],{},[14,159,40],{},[14,161,162,163,165],{},"讲解：与 37.1 相同，候选码为 ",[31,164,46],{},"，决定因素是超码。",[26,167,169,170,34,173],{"id":168},"_376-rw-x-y-zfx-z-wx-y","37.6 ",[31,171,172],{},"R(W, X, Y, Z)",[31,174,175],{},"F={X -> Z, WX -> Y}",[14,177,178],{},"答案：1NF，不满足 2NF。",[14,180,43,181,184,185,188,189,191,192,194],{},[31,182,183],{},"WX","，因为 ",[31,186,187],{},"WX+ = WXYZ","。非主属性 ",[31,190,83],{}," 依赖于候选码的一部分 ",[31,193,76],{},"，存在部分依赖，所以不满足 2NF。",[18,196,198,199,202,203,34,206,209],{"id":197},"_38-有关系模式-ru-f其中-ua-b-c-d-e-pfa-b-c-p-e-a-ce-d求-r-的所有候选关键字","38. 有关系模式 ",[31,200,201],{},"R(U, F)","，其中 ",[31,204,205],{},"U={A, B, C, D, E, P}",[31,207,208],{},"F={A -> B, C -> P, E -> A, CE -> D}","。求 R 的所有候选关键字。",[14,211,212,213,216],{},"答案：",[31,214,215],{},"CE","。",[14,218,108],{},[220,221,222,233,239],"ul",{},[223,224,225,226,69,229,232],"li",{},"没有出现在任何依赖右部的属性是 ",[31,227,228],{},"C",[31,230,231],{},"E","，它们必须出现在每个候选码中。",[223,234,235,238],{},[31,236,237],{},"(CE)+ = C E P A B D","，可推出全部属性。",[223,240,241,34,244,247],{},[31,242,243],{},"C+ = CP",[31,245,246],{},"E+ = EAB","，都不能推出全部属性。",[14,249,250,251,216],{},"因此唯一候选码是 ",[31,252,215],{},[18,254,256,257,260,261,209],{"id":255},"_39-设有关系模式-rc-t-s-n-g函数依赖集-fc-t-cs-g-s-n求-r-的所有候选关键字","39. 设有关系模式 ",[31,258,259],{},"R(C, T, S, N, G)","，函数依赖集 ",[31,262,263],{},"F={C -> T, CS -> G, S -> N}",[14,265,212,266,216],{},[31,267,268],{},"CS",[14,270,271,272,69,274,277,278,281,282,34,285,288,289,216],{},"讲解：没有出现在右部的属性是 ",[31,273,228],{},[31,275,276],{},"S","，所以候选码必须包含它们。",[31,279,280],{},"(CS)+ = C S T G N","，可以推出全部属性；",[31,283,284],{},"C+ = CT",[31,286,287],{},"S+ = SN"," 都不行。因此唯一候选码为 ",[31,290,268],{},[18,292,294,295,34,298,34,301,304],{"id":293},"_40-设-rufuabcdfa-b-b-c-d-b把-r-分解成-bcnf-模式集","40. 设 ",[31,296,297],{},"R(U,F)",[31,299,300],{},"U={A,B,C,D}",[31,302,303],{},"F={A -> B, B -> C, D -> B}","，把 R 分解成 BCNF 模式集。",[26,306,308,309,312],{"id":307},"_401-如果首先把-r-分解成-acd-bd求-f-在这两个模式上的投影","40.1 如果首先把 R 分解成 ",[31,310,311],{},"{ACD, BD}","，求 F 在这两个模式上的投影。",[14,314,212],{},[220,316,317,330],{},[223,318,319,320,323,324,34,327,216],{},"在 ",[31,321,322],{},"ACD"," 上的投影：",[31,325,326],{},"A -> C",[31,328,329],{},"D -> C",[223,331,319,332,323,335,216],{},[31,333,334],{},"BD",[31,336,337],{},"D -> B",[14,339,108,340,342,343,346,347,342,349,352,353,355,356,216],{},[31,341,326],{}," 由 ",[31,344,345],{},"A -> B -> C"," 推出；",[31,348,329],{},[31,350,351],{},"D -> B -> C"," 推出。",[31,354,334],{}," 上只保留涉及 B、D 的依赖，得到 ",[31,357,337],{},[26,359,361,362,69,364,366],{"id":360},"_402-acd-和-bd-是-bcnf-吗如果不是进一步分解","40.2 ",[31,363,322],{},[31,365,334],{}," 是 BCNF 吗？如果不是，进一步分解。",[14,368,212],{},[220,370,371,385],{},[223,372,373,375,376,88,378,381,382,384],{},[31,374,334],{}," 是 BCNF，因为 ",[31,377,337],{},[31,379,380],{},"D"," 是 ",[31,383,334],{}," 的候选码。",[223,386,387,389,390,392,393,396,397,77,399,401],{},[31,388,322],{}," 不是 BCNF。",[31,391,322],{}," 的候选码为 ",[31,394,395],{},"AD","，而 ",[31,398,326],{},[31,400,329],{}," 的左部都不是超码。",[14,403,404],{},"一种 BCNF 分解为：",[220,406,407,412,417],{},[223,408,409],{},[31,410,411],{},"AC(A, C)",[223,413,414],{},[31,415,416],{},"AD(A, D)",[223,418,419],{},[31,420,421],{},"BD(B, D)",[14,423,424,425,88,428,431,432,434,435,437],{},"讲解：在 ",[31,426,427],{},"AC",[31,429,430],{},"A"," 是码，满足 BCNF；",[31,433,395],{}," 上没有非平凡函数依赖，满足 BCNF；",[31,436,334],{}," 已满足 BCNF。",[18,439,441,442,445,446,449],{"id":440},"_41-已知关系模式-rcity-st-zip-和函数依赖集-fcity-st-zip-zip-city找出-r-的两个候选关键字","41. 已知关系模式 ",[31,443,444],{},"R(CITY, ST, ZIP)"," 和函数依赖集 ",[31,447,448],{},"F={CITY, ST -> ZIP; ZIP -> CITY}","。找出 R 的两个候选关键字。",[14,451,212,452,69,455,216],{},[31,453,454],{},"(CITY, ST)",[31,456,457],{},"(ZIP, ST)",[14,459,108],{},[220,461,462,467,472],{},[223,463,464,216],{},[31,465,466],{},"(CITY, ST)+ = CITY, ST, ZIP",[223,468,469,216],{},[31,470,471],{},"(ZIP, ST)+ = ZIP, ST, CITY",[223,473,474,475,478,479,482,483,486,487,489,490,492],{},"单独 ",[31,476,477],{},"ZIP"," 只能推出 ",[31,480,481],{},"CITY","，不能推出 ",[31,484,485],{},"ST","；单独 ",[31,488,481],{}," 或 ",[31,491,485],{}," 也不能推出全部属性。",[14,494,495,496,498,499,216],{},"因此两个候选码是 ",[31,497,454],{}," 与 ",[31,500,457],{},[18,502,504,505,508,509,512,513,516,517,520,521,216],{"id":503},"_42-教师管理数据库属性为学号-s课程号-c成绩-g任课教师-tn教师所在系-d","42. 教师管理数据库：属性为学号 ",[31,506,507],{},"S#","、课程号 ",[31,510,511],{},"C#","、成绩 ",[31,514,515],{},"G","、任课教师 ",[31,518,519],{},"TN","、教师所在系 ",[31,522,380],{},[14,524,525],{},"语义：",[527,528,529,532,535,538],"ol",{},[223,530,531],{},"学号和课程分别与其代表的学生和课程一一对应。",[223,533,534],{},"一个学生所修的每门课程都有一个成绩。",[223,536,537],{},"每门课程只有一位任课教师，但每位教师可以有多门课程。",[223,539,540],{},"教师没有重名，每个教师只属于一个系。",[26,542,544],{"id":543},"_421-确定函数依赖集","42.1 确定函数依赖集。",[14,546,212],{},[220,548,549,554,559],{},[223,550,551],{},[31,552,553],{},"(S#, C#) -> G",[223,555,556],{},[31,557,558],{},"C# -> TN",[223,560,561],{},[31,562,563],{},"TN -> D",[14,565,566,567,216],{},"由后两条还可推出 ",[31,568,569],{},"C# -> D",[26,571,573],{"id":572},"_422-若用所有属性组成一个模式该关系模式为几范式并说明异常","42.2 若用所有属性组成一个模式，该关系模式为几范式？并说明异常。",[14,575,576],{},"答案：该模式为 1NF，不满足 2NF。",[14,578,579,580,583,584,586,587,589,590,592,593,596],{},"讲解：候选码是 ",[31,581,582],{},"(S#, C#)","。因为 ",[31,585,558],{},"，非主属性 ",[31,588,519],{}," 部分依赖于组合码的一部分 ",[31,591,511],{},"，所以不满足 2NF；同时还有 ",[31,594,595],{},"C# -> TN -> D"," 的传递依赖。",[14,598,599],{},"异常示例：",[220,601,602,605,608],{},[223,603,604],{},"插入异常：一门新课程已有任课教师但还没有学生选课时，无法单独插入课程-教师信息。",[223,606,607],{},"删除异常：删除某课程最后一条选课记录，可能丢失该课程任课教师及教师所在系信息。",[223,609,610],{},"修改异常：教师所在系重复出现在很多选课记录中，修改时容易不一致。",[26,612,614],{"id":613},"_423-分解为依赖保持无损连接的-3nf","42.3 分解为依赖保持、无损连接的 3NF。",[14,616,212],{},[220,618,619,624,629],{},[223,620,621],{},[31,622,623],{},"SC(S#, C#, G)",[223,625,626],{},[31,627,628],{},"CT(C#, TN)",[223,630,631],{},[31,632,633],{},"TD(TN, D)",[14,635,108,636,639,640,643,644,647],{},[31,637,638],{},"SC"," 保存选课成绩，",[31,641,642],{},"CT"," 保存课程教师，",[31,645,646],{},"TD"," 保存教师所在系。三个原始依赖都被保留，并且可通过外键连接恢复原关系。",[18,649,651,652,655],{"id":650},"_43-给出关系-r工程号-材料号-数量-开工日期-完工日期-价格判断范式并分解","43. 给出关系 ",[31,653,654],{},"R(工程号, 材料号, 数量, 开工日期, 完工日期, 价格)","，判断范式并分解。",[14,657,658],{},"题面关系：",[660,661,662,687],"table",{},[663,664,665],"thead",{},[666,667,668,672,675,678,681,684],"tr",{},[669,670,671],"th",{},"工程号",[669,673,674],{},"材料号",[669,676,677],{},"数量",[669,679,680],{},"开工日期",[669,682,683],{},"完工日期",[669,685,686],{},"价格",[688,689,690,711,728,745,762],"tbody",{},[666,691,692,696,699,702,705,708],{},[693,694,695],"td",{},"P1",[693,697,698],{},"I1",[693,700,701],{},"4",[693,703,704],{},"9805",[693,706,707],{},"9902",[693,709,710],{},"250",[666,712,713,715,718,721,723,725],{},[693,714,695],{},[693,716,717],{},"I2",[693,719,720],{},"6",[693,722,704],{},[693,724,707],{},[693,726,727],{},"300",[666,729,730,732,735,738,740,742],{},[693,731,695],{},[693,733,734],{},"I3",[693,736,737],{},"15",[693,739,704],{},[693,741,707],{},[693,743,744],{},"180",[666,746,747,750,752,754,757,760],{},[693,748,749],{},"P2",[693,751,698],{},[693,753,720],{},[693,755,756],{},"9811",[693,758,759],{},"9912",[693,761,710],{},[666,763,764,766,769,772,774,776],{},[693,765,749],{},[693,767,768],{},"I4",[693,770,771],{},"18",[693,773,756],{},[693,775,759],{},[693,777,778],{},"350",[14,780,212],{},[220,782,783,789,809],{},[223,784,785,786,216],{},"候选码：",[31,787,788],{},"(工程号, 材料号)",[223,790,791,792],{},"函数依赖：\n",[220,793,794,799,804],{},[223,795,796],{},[31,797,798],{},"工程号 -> 开工日期, 完工日期",[223,800,801],{},[31,802,803],{},"材料号 -> 价格",[223,805,806],{},[31,807,808],{},"(工程号, 材料号) -> 数量",[223,810,811],{},"该关系为 1NF，不满足 2NF，因为存在非主属性对组合码的部分依赖。",[14,813,814],{},"分解为：",[220,816,817,822,827],{},[223,818,819],{},[31,820,821],{},"工程(工程号, 开工日期, 完工日期)",[223,823,824],{},[31,825,826],{},"材料(材料号, 价格)",[223,828,829],{},[31,830,831],{},"用料(工程号, 材料号, 数量)",[14,833,834],{},"讲解：分解后，工程日期只存一次，材料价格只存一次，用料数量存放在工程和材料的联系表中，可避免更新、插入、删除异常。",[18,836,838],{"id":837},"_44-判断给出的数据库集是否可直接作为关系数据库中的关系若不行改造为尽可能好的关系形式","44. 判断给出的数据库集是否可直接作为关系数据库中的关系；若不行，改造为尽可能好的关系形式。",[14,840,841],{},"题面表：",[660,843,844,857],{},[663,845,846],{},[666,847,848,851,854],{},[669,849,850],{},"系名",[669,852,853],{},"课程名",[669,855,856],{},"教师名",[688,858,859,870,881,892],{},[666,860,861,864,867],{},[693,862,863],{},"计算机系",[693,865,866],{},"DB",[693,868,869],{},"李军，刘强",[666,871,872,875,878],{},[693,873,874],{},"机械系",[693,876,877],{},"CAD",[693,879,880],{},"金山，宋海",[666,882,883,886,889],{},[693,884,885],{},"造船系",[693,887,888],{},"CAM",[693,890,891],{},"王华",[666,893,894,897,900],{},[693,895,896],{},"自控系",[693,898,899],{},"CTY",[693,901,902],{},"张红，曾键",[14,904,212],{},[14,906,907],{},"不能直接作为关系数据库中的关系，因为“教师名”列中有多个教师名，属性值不是原子的，违反 1NF。",[14,909,910],{},"一种改造方式：",[660,912,913,923],{},[663,914,915],{},[666,916,917,919,921],{},[669,918,850],{},[669,920,853],{},[669,922,856],{},[688,924,925,934,943,952,961,969,978],{},[666,926,927,929,931],{},[693,928,863],{},[693,930,866],{},[693,932,933],{},"李军",[666,935,936,938,940],{},[693,937,863],{},[693,939,866],{},[693,941,942],{},"刘强",[666,944,945,947,949],{},[693,946,874],{},[693,948,877],{},[693,950,951],{},"金山",[666,953,954,956,958],{},[693,955,874],{},[693,957,877],{},[693,959,960],{},"宋海",[666,962,963,965,967],{},[693,964,885],{},[693,966,888],{},[693,968,891],{},[666,970,971,973,975],{},[693,972,896],{},[693,974,899],{},[693,976,977],{},"张红",[666,979,980,982,984],{},[693,981,896],{},[693,983,899],{},[693,985,986],{},"曾键",[14,988,989],{},"更规范的关系模式可设计为：",[220,991,992,997,1002],{},[223,993,994],{},[31,995,996],{},"系(系名)",[223,998,999],{},[31,1000,1001],{},"课程(课程名, 系名)",[223,1003,1004],{},[31,1005,1006],{},"授课(课程名, 教师名)",[14,1008,1009],{},"讲解：先让每个属性值原子化，再根据业务语义继续分解，避免把多值属性塞进一个单元格。",[18,1011,1013,1014,1017],{"id":1012},"_45-设关系-r课程名-教师名-教师地址判断范式删除异常并分解","45. 设关系 ",[31,1015,1016],{},"R(课程名, 教师名, 教师地址)","，判断范式、删除异常，并分解。",[14,1019,658],{},[660,1021,1022,1033],{},[663,1023,1024],{},[666,1025,1026,1028,1030],{},[669,1027,853],{},[669,1029,856],{},[669,1031,1032],{},"教师地址",[688,1034,1035,1046,1056,1067],{},[666,1036,1037,1040,1043],{},[693,1038,1039],{},"C1",[693,1041,1042],{},"马千里",[693,1044,1045],{},"D1",[666,1047,1048,1051,1054],{},[693,1049,1050],{},"C2",[693,1052,1053],{},"于得水",[693,1055,1045],{},[666,1057,1058,1061,1064],{},[693,1059,1060],{},"C3",[693,1062,1063],{},"余快",[693,1065,1066],{},"D2",[666,1068,1069,1072,1074],{},[693,1070,1071],{},"C4",[693,1073,1053],{},[693,1075,1045],{},[14,1077,212],{},[220,1079,1080,1083,1092,1096],{},[223,1081,1082],{},"假定一门课程只有一位教师，教师只有一个地址。",[223,1084,1085,1086,34,1089,216],{},"函数依赖：",[31,1087,1088],{},"课程名 -> 教师名",[31,1090,1091],{},"教师名 -> 教师地址",[223,1093,785,1094,216],{},[31,1095,853],{},[223,1097,1098,1099,216],{},"该关系满足 2NF，但不满足 3NF，因为存在传递依赖 ",[31,1100,1101],{},"课程名 -> 教师名 -> 教师地址",[14,1103,1104],{},"删除异常：若删除于得水老师所教的最后一门课程，会同时丢失“于得水住址为 D1”的信息。",[14,1106,814],{},[220,1108,1109,1114],{},[223,1110,1111],{},[31,1112,1113],{},"课程教师(课程名, 教师名)",[223,1115,1116],{},[31,1117,1118],{},"教师地址(教师名, 教师地址)",[14,1120,1121,1122,1124],{},"讲解：分解后，即使某教师暂时没有课程，也可以在 ",[31,1123,1032],{}," 中保存教师基本信息。",[18,1126,1128,1129,1132],{"id":1127},"_46-设关系-r职工号-职工名-年龄-性别-单位号-单位名判断是否属于-3nf若不是规范化为-3nf","46. 设关系 ",[31,1130,1131],{},"R(职工号, 职工名, 年龄, 性别, 单位号, 单位名)","，判断是否属于 3NF；若不是，规范化为 3NF。",[14,1134,658],{},[660,1136,1137,1159],{},[663,1138,1139],{},[666,1140,1141,1144,1147,1150,1153,1156],{},[669,1142,1143],{},"职工号",[669,1145,1146],{},"职工名",[669,1148,1149],{},"年龄",[669,1151,1152],{},"性别",[669,1154,1155],{},"单位号",[669,1157,1158],{},"单位名",[688,1160,1161,1181,1200,1217],{},[666,1162,1163,1166,1169,1172,1175,1178],{},[693,1164,1165],{},"E1",[693,1167,1168],{},"ZHAO",[693,1170,1171],{},"20",[693,1173,1174],{},"F",[693,1176,1177],{},"D3",[693,1179,1180],{},"CCC",[666,1182,1183,1186,1189,1192,1195,1197],{},[693,1184,1185],{},"E2",[693,1187,1188],{},"QIAN",[693,1190,1191],{},"25",[693,1193,1194],{},"M",[693,1196,1045],{},[693,1198,1199],{},"AAA",[666,1201,1202,1205,1208,1211,1213,1215],{},[693,1203,1204],{},"E3",[693,1206,1207],{},"SEN",[693,1209,1210],{},"38",[693,1212,1194],{},[693,1214,1177],{},[693,1216,1180],{},[666,1218,1219,1221,1224,1226,1228,1230],{},[693,1220,1204],{},[693,1222,1223],{},"LI",[693,1225,1191],{},[693,1227,1174],{},[693,1229,1177],{},[693,1231,1180],{},[14,1233,212],{},[14,1235,1236,1237,1239],{},"若按常规语义“职工号唯一标识职工”，题面数据中 ",[31,1238,1204],{}," 出现两次且姓名、年龄、性别不同，已经违反实体完整性。忽略该录入错误后，函数依赖可写为：",[220,1241,1242,1247],{},[223,1243,1244],{},[31,1245,1246],{},"职工号 -> 职工名, 年龄, 性别, 单位号",[223,1248,1249],{},[31,1250,1251],{},"单位号 -> 单位名",[14,1253,785,1254,216],{},[31,1255,1143],{},[14,1257,1258,1259,216],{},"该关系不属于 3NF，属于 2NF。原因是候选码为单属性，不存在部分依赖；但存在传递依赖 ",[31,1260,1261],{},"职工号 -> 单位号 -> 单位名",[14,1263,1264],{},"3NF 分解：",[220,1266,1267,1272],{},[223,1268,1269],{},[31,1270,1271],{},"职工(职工号, 职工名, 年龄, 性别, 单位号)",[223,1273,1274],{},[31,1275,1276],{},"单位(单位号, 单位名)",[14,1278,1279],{},"讲解：单位名是单位的属性，不应在每个职工元组中重复保存。",[18,1281,1283,1284,1287],{"id":1282},"_47-给出关系-scsno-cno-ctitle-iname-iloca-grade判断范式和异常并分解","47. 给出关系 ",[31,1285,1286],{},"SC(SNO, CNO, CTITLE, INAME, ILOCA, GRADE)","，判断范式和异常，并分解。",[14,1289,658],{},[660,1291,1292,1314],{},[663,1293,1294],{},[666,1295,1296,1299,1302,1305,1308,1311],{},[669,1297,1298],{},"SNO",[669,1300,1301],{},"CNO",[669,1303,1304],{},"CTITLE",[669,1306,1307],{},"INAME",[669,1309,1310],{},"ILOCA",[669,1312,1313],{},"GRADE",[688,1315,1316,1334,1351,1367,1384],{},[666,1317,1318,1321,1323,1326,1329,1331],{},[693,1319,1320],{},"80152",[693,1322,1039],{},[693,1324,1325],{},"OS",[693,1327,1328],{},"王平",[693,1330,1045],{},[693,1332,1333],{},"70",[666,1335,1336,1339,1341,1343,1346,1348],{},[693,1337,1338],{},"80153",[693,1340,1050],{},[693,1342,866],{},[693,1344,1345],{},"高升",[693,1347,1066],{},[693,1349,1350],{},"85",[666,1352,1353,1356,1358,1360,1362,1364],{},[693,1354,1355],{},"80154",[693,1357,1039],{},[693,1359,1325],{},[693,1361,1328],{},[693,1363,1045],{},[693,1365,1366],{},"86",[666,1368,1369,1371,1373,1376,1379,1381],{},[693,1370,1355],{},[693,1372,1060],{},[693,1374,1375],{},"AI",[693,1377,1378],{},"杨杨",[693,1380,1177],{},[693,1382,1383],{},"72",[666,1385,1386,1389,1391,1394,1396,1398],{},[693,1387,1388],{},"80155",[693,1390,1071],{},[693,1392,1393],{},"CL",[693,1395,1345],{},[693,1397,1066],{},[693,1399,1400],{},"92",[14,1402,1403,1404,1406,1407,1409,1410,1412,1413,1415,1416,1418,1419,1421],{},"属性含义：",[31,1405,1298],{}," 学号，",[31,1408,1301],{}," 课程号，",[31,1411,1304],{}," 课程名，",[31,1414,1307],{}," 教师名，",[31,1417,1310],{}," 教师地址，",[31,1420,1313],{}," 成绩。",[14,1423,212],{},[220,1425,1426,1431,1450],{},[223,1427,785,1428,216],{},[31,1429,1430],{},"(SNO, CNO)",[223,1432,791,1433],{},[220,1434,1435,1440,1445],{},[223,1436,1437],{},[31,1438,1439],{},"(SNO, CNO) -> GRADE",[223,1441,1442],{},[31,1443,1444],{},"CNO -> CTITLE, INAME",[223,1446,1447],{},[31,1448,1449],{},"INAME -> ILOCA",[223,1451,1452,1453,77,1455,77,1457,1459,1460,216],{},"该关系为 1NF，不满足 2NF，因为 ",[31,1454,1304],{},[31,1456,1307],{},[31,1458,1310],{}," 部分依赖于组合码中的 ",[31,1461,1301],{},[14,1463,1464],{},"异常：",[220,1466,1467,1470,1473],{},[223,1468,1469],{},"插入异常：新开课程还没有学生选课时，无法保存课程名、教师和教师地址。",[223,1471,1472],{},"删除异常：删除某课程最后一条选课记录时，会丢失课程和教师信息。",[223,1474,1475],{},"修改异常：教师地址重复保存，修改时可能不一致。",[14,1477,1478],{},"分解到 2NF：",[220,1480,1481,1486],{},[223,1482,1483],{},[31,1484,1485],{},"选课(SNO, CNO, GRADE)",[223,1487,1488],{},[31,1489,1490],{},"课程任课(CNO, CTITLE, INAME, ILOCA)",[14,1492,1493],{},"进一步分解到 3NF：",[220,1495,1496,1500,1505],{},[223,1497,1498],{},[31,1499,1485],{},[223,1501,1502],{},[31,1503,1504],{},"课程任课(CNO, CTITLE, INAME)",[223,1506,1507],{},[31,1508,1509],{},"教师(INAME, ILOCA)",[14,1511,1512,1513,1516,1517,1520],{},"讲解：只分解到 2NF 后，",[31,1514,1515],{},"课程任课"," 中仍有 ",[31,1518,1519],{},"CNO -> INAME -> ILOCA"," 的传递依赖。继续分解到 3NF 才能更好消除教师地址冗余。",{"title":1522,"searchDepth":1523,"depth":1523,"links":1524},"",2,[1525,1540,1542,1544,1551,1553,1559,1561,1562,1564,1566],{"id":20,"depth":1523,"text":21,"children":1526},[1527,1530,1532,1534,1536,1538],{"id":28,"depth":1528,"text":1529},3,"37.1 R(X, Y, Z)，F={XY -> Z}",{"id":54,"depth":1528,"text":1531},"37.2 R(X, Y, Z)，F={Y -> Z, XZ -> Y}",{"id":97,"depth":1528,"text":1533},"37.3 R(X, Y, Z)，F={X -> Y, Y -> X, X -> YZ}",{"id":130,"depth":1528,"text":1535},"37.4 R(X, Y, Z)，F={X -> Y, X -> Z}",{"id":152,"depth":1528,"text":1537},"37.5 R(X, Y, Z)，F={XY -> Z}",{"id":168,"depth":1528,"text":1539},"37.6 R(W, X, Y, Z)，F={X -> Z, WX -> Y}",{"id":197,"depth":1523,"text":1541},"38. 有关系模式 R(U, F)，其中 U={A, B, C, D, E, P}，F={A -> B, C -> P, E -> A, CE -> D}。求 R 的所有候选关键字。",{"id":255,"depth":1523,"text":1543},"39. 设有关系模式 R(C, T, S, N, G)，函数依赖集 F={C -> T, CS -> G, S -> N}。求 R 的所有候选关键字。",{"id":293,"depth":1523,"text":1545,"children":1546},"40. 设 R(U,F)，U={A,B,C,D}，F={A -> B, B -> C, D -> B}，把 R 分解成 BCNF 模式集。",[1547,1549],{"id":307,"depth":1528,"text":1548},"40.1 如果首先把 R 分解成 {ACD, BD}，求 F 在这两个模式上的投影。",{"id":360,"depth":1528,"text":1550},"40.2 ACD 和 BD 是 BCNF 吗？如果不是，进一步分解。",{"id":440,"depth":1523,"text":1552},"41. 已知关系模式 R(CITY, ST, ZIP) 和函数依赖集 F={CITY, ST -> ZIP; ZIP -> CITY}。找出 R 的两个候选关键字。",{"id":503,"depth":1523,"text":1554,"children":1555},"42. 教师管理数据库：属性为学号 S#、课程号 C#、成绩 G、任课教师 TN、教师所在系 D。",[1556,1557,1558],{"id":543,"depth":1528,"text":544},{"id":572,"depth":1528,"text":573},{"id":613,"depth":1528,"text":614},{"id":650,"depth":1523,"text":1560},"43. 给出关系 R(工程号, 材料号, 数量, 开工日期, 完工日期, 价格)，判断范式并分解。",{"id":837,"depth":1523,"text":838},{"id":1012,"depth":1523,"text":1563},"45. 设关系 R(课程名, 教师名, 教师地址)，判断范式、删除异常，并分解。",{"id":1127,"depth":1523,"text":1565},"46. 设关系 R(职工号, 职工名, 年龄, 性别, 单位号, 单位名)，判断是否属于 3NF；若不是，规范化为 3NF。",{"id":1282,"depth":1523,"text":1567},"47. 给出关系 SC(SNO, CNO, CTITLE, INAME, ILOCA, GRADE)，判断范式和异常，并分解。","md",{},true,"\u002Fsource\u002Fcs\u002Fdb\u002F100+70\u002Fday10-70-37-47",{"title":5,"description":16},"source\u002Fcs\u002Fdb\u002F100+70\u002FDay10-数据库70题-综合37-47","L7m0im9i_Y1VFrN20f4zbPtR_X5kQm_wC0iYqKSvicg",1793692175096]