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<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8"> <meta name="generator" content="pdf2htmlEX"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <link rel="stylesheet" href="https://static.pudn.com/base/css/base.min.css"> <link rel="stylesheet" href="https://static.pudn.com/base/css/fancy.min.css"> <link rel="stylesheet" href="https://static.pudn.com/prod/directory_preview_static/6275d27d602a7856fed4e5a3/raw.css"> <script src="https://static.pudn.com/base/js/compatibility.min.js"></script> <script src="https://static.pudn.com/base/js/pdf2htmlEX.min.js"></script> <script> try{ pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({}); }catch(e){} </script> <title></title> </head> <body> <div id="sidebar" style="display: none"> <div id="outline"> </div> </div> <div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6275d27d602a7856fed4e5a3/bg1.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 x1 h3 y2 ff1 fs0 fc0 sc0 ls0 ws0">数据库设计</div><div class="t m0 x2 h4 y3 ff2 fs1 fc0 sc1 ls0 ws0">Ⅰ<span class="ff3">. <span class="ff1 sc0">数据库设计原则</span></span></div><div class="t m0 x2 h4 y4 ff4 fs1 fc0 sc1 ls0 ws0">1.<span class="_ _0"> </span><span class="ff1">所设计出来的数据库表格要很好的<span class="fc1">反映客观现实</span>。</span></div><div class="t m0 x2 h4 y5 ff4 fs1 fc0 sc1 ls0 ws0">2.<span class="_ _0"> </span><span class="ff1">各表之间的<span class="fc1">关联</span>要<span class="fc1">明确、清晰</span>。</span></div><div class="t m0 x2 h4 y6 ff4 fs1 fc0 sc1 ls0 ws0">3.<span class="_ _0"> </span><span class="ff1">尽量<span class="fc1">减少冗余</span>。</span></div><div class="t m0 x2 h4 y7 ff4 fs1 fc0 sc1 ls0 ws0">4.<span class="_ _0"> </span><span class="ff1">主键设计：</span></div><div class="t m0 x3 h4 y8 ff4 fs1 fc0 sc1 ls0 ws0">1<span class="_ _1"> </span><span class="ff1">尽量使用<span class="fc1">单主键</span>，少用联合主键；</span></div><div class="t m0 x3 h4 y9 ff4 fs1 fc0 sc1 ls0 ws0">2<span class="_ _1"> </span><span class="ff1">一般<span class="_ _2"></span><span class="fc1">不要</span>使<span class="_ _2"></span>用<span class="fc1">业<span class="_ _2"></span>务属性<span class="_ _2"></span></span>作为<span class="_ _2"></span><span class="fc1">主键<span class="_ _2"></span></span>（如果<span class="_ _2"></span>修改该主<span class="_ _2"></span>键时，对<span class="_ _2"></span>引用该<span class="_ _2"></span>属性的</span></div><div class="t m0 x4 h4 ya ff1 fs1 fc0 sc1 ls0 ws0">数据的修改将带来麻烦）。</div><div class="t m0 x3 h4 yb ff4 fs2 fc0 sc1 ls0 ws0">③<span class="ff5"> <span class="_ _3"></span><span class="ff1 fs1">主<span class="_ _2"></span>关<span class="_ _2"></span>键<span class="_ _2"></span>字<span class="_ _2"></span>的长<span class="_ _2"></span>度<span class="_ _2"></span>直<span class="_ _2"></span>接<span class="_ _2"></span>影<span class="_ _2"></span>响<span class="_ _2"></span>数<span class="_ _2"></span>据<span class="_ _2"></span>库<span class="_ _2"></span>的<span class="_ _2"></span>操<span class="_ _2"></span>作<span class="_ _2"></span>速<span class="_ _2"></span>度<span class="_ _2"></span>，<span class="_ _2"></span>因<span class="_ _2"></span>此<span class="_ _2"></span>在<span class="_ _2"></span>创<span class="_ _2"></span>建<span class="_ _2"></span>主<span class="_ _2"></span>关<span class="_ _2"></span>键<span class="_ _2"></span>字<span class="_ _2"></span>段时<span class="_ _4"></span>，</span></span></div><div class="t m0 x5 h4 yc ff1 fs1 fc0 sc1 ls0 ws0">该字段值最好使用能满足存储要求的最小长度。<span class="ff5"> </span></div><div class="t m0 x2 h4 yd ff4 fs1 fc0 sc1 ls0 ws0">5.<span class="_ _0"> </span><span class="ff1">在设计的过程中要考虑对数据的操作问题。</span></div><div class="t m0 x2 h4 ye ff2 fs1 fc0 sc1 ls0 ws0">Ⅱ. <span class="ff1 sc0">数据库设计步骤</span></div><div class="t m0 x2 h5 yf ff6 fs1 fc1 sc1 ls0 ws0">1.</div><div class="t m1 x6 h6 yf ff1 fs3 fc1 sc1 ls0 ws0">分析数据需求</div><div class="t m0 x6 h4 y10 ff1 fs1 fc0 sc1 ls0 ws0">明确需要从数据库中得到哪些信息。明确目的之后，就可以确定需要保存哪</div><div class="t m0 x6 h4 y11 ff1 fs1 fc0 sc1 ls0 ws0">些主题的信息（表）。</div><div class="t m0 x2 h7 y12 ff7 fs1 fc1 sc1 ls0 ws0">2.</div><div class="t m1 x6 h6 y12 ff1 fs3 fc1 sc1 ls0 ws0">将需求分类放入表</div><div class="t m0 x3 h4 y13 ff1 fs1 fc0 sc1 ls0 ws0">请<span class="_ _2"></span>仔<span class="_ _2"></span>细<span class="_ _2"></span>研<span class="_ _2"></span>究需<span class="_ _2"></span>要<span class="_ _2"></span>从<span class="_ _2"></span>数<span class="_ _2"></span>据<span class="_ _2"></span>库<span class="_ _2"></span>中<span class="_ _2"></span>取<span class="_ _2"></span>出<span class="_ _2"></span>的<span class="_ _2"></span>信<span class="_ _2"></span>息<span class="_ _4"></span>后<span class="_ _2"></span>，<span class="_ _2"></span>并<span class="_ _2"></span>把<span class="_ _2"></span>这<span class="_ _2"></span>些信<span class="_ _2"></span>息<span class="_ _2"></span>分<span class="_ _2"></span>成<span class="_ _2"></span>各<span class="_ _2"></span>种<span class="_ _2"></span>基<span class="_ _2"></span>本<span class="_ _2"></span>主</div><div class="t m0 x3 h4 y14 ff1 fs1 fc0 sc1 ls0 ws0">题<span class="_ _2"></span>（<span class="_ _2"></span>例<span class="_ _2"></span>如<span class="_ _2"></span>顾客<span class="_ _2"></span>、<span class="_ _2"></span>雇<span class="_ _2"></span>员<span class="_ _2"></span>、<span class="_ _2"></span>销<span class="_ _2"></span>售<span class="_ _2"></span>的<span class="_ _2"></span>产<span class="_ _2"></span>品<span class="_ _2"></span>、<span class="_ _2"></span>提<span class="_ _2"></span>供<span class="_ _2"></span>的<span class="_ _2"></span>服<span class="_ _2"></span>务<span class="_ _2"></span>等<span class="_ _2"></span>等<span class="_ _2"></span>）<span class="_ _2"></span>，<span class="_ _2"></span>每<span class="_ _2"></span>个<span class="_ _2"></span>主<span class="_ _2"></span>题<span class="_ _2"></span>都是<span class="_ _2"></span>一</div><div class="t m0 x3 h4 y15 ff1 fs1 fc0 sc1 ls0 ws0">个独立的表。</div><div class="t m0 x2 h8 y16 ff5 fs1 fc1 sc1 ls0 ws0">3. </div><div class="t m1 x7 h6 y16 ff1 fs3 fc1 sc1 ls0 ws0">确定所需字段</div><div class="t m0 x2 h4 y17 ff4 fs1 fc0 sc1 ls0 ws0">①<span class="ff5"> <span class="_ _2"></span><span class="ff1">每个<span class="_ _2"></span>字段<span class="_ _2"></span>直接<span class="_ _2"></span>和表<span class="_ _2"></span>的主题<span class="_ _2"></span>相关<span class="_ _3"></span>：确<span class="_ _2"></span>保一个<span class="_ _2"></span>表中<span class="_ _2"></span>的每<span class="_ _2"></span>个字<span class="_ _2"></span>段直接<span class="_ _2"></span>描述<span class="_ _2"></span>该表<span class="_ _2"></span>的主</span></span></div><div class="t m0 x2 h4 y18 ff1 fs1 fc0 sc1 ls0 ws0">题。如果多个表中重复同样的信息，这表明在某些表中有不必要的字段；</div><div class="t m0 x2 h4 y19 ff4 fs1 fc0 sc1 ls0 ws0">②<span class="ff5"> <span class="ff1">不要包含可推导得到或需计算的数据；</span></span></div><div class="t m0 x2 h4 y1a ff4 fs1 fc0 sc1 ls0 ws0">③<span class="ff5"> <span class="_ _2"></span><span class="ff1">收集<span class="_ _2"></span>所需<span class="_ _2"></span>的全<span class="_ _2"></span>部信<span class="_ _2"></span>息：<span class="_ _2"></span>检查<span class="_ _2"></span>书面<span class="_ _2"></span>的表<span class="_ _2"></span>单和<span class="_ _2"></span>报表<span class="_ _2"></span>，确<span class="_ _2"></span>保过<span class="_ _2"></span>去所<span class="_ _2"></span>需的信<span class="_ _2"></span>息都<span class="_ _2"></span>已包</span></span></div><div class="t m0 x2 h4 y1b ff1 fs1 fc0 sc1 ls0 ws0">括在<span class="ff5"> V<span class="_ _5"></span>isual FoxPro <span class="ff1">表中，或者可由这些表计算出来；</span></span></div><div class="t m0 x2 h4 y1c ff4 fs1 fc0 sc1 ls0 ws0">④<span class="ff5"> <span class="_ _2"></span><span class="ff1">以最<span class="_ _2"></span>小的<span class="_ _2"></span>逻辑<span class="_ _2"></span>单位<span class="_ _2"></span>存储信<span class="_ _2"></span>息<span class="_ _2"></span>：<span class="_ _2"></span>如，<span class="_ _2"></span>为产<span class="_ _2"></span>品名<span class="_ _2"></span>、产<span class="_ _2"></span>品类别<span class="_ _2"></span>和产<span class="_ _2"></span>品描<span class="_ _2"></span>述创建<span class="_ _2"></span>不同</span></span></div><div class="t m0 x2 h4 y1d ff1 fs1 fc0 sc1 ls0 ws0">的字段。</div><div class="t m0 x2 h8 y1e ff5 fs1 fc1 sc1 ls0 ws0">4.</div><div class="t m1 x8 h6 y1e ff1 fs3 fc1 sc1 ls0 ws0">确定各表的主键</div></div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div> </body> </html>