<ruby id="bdb3f"></ruby>

    <p id="bdb3f"><cite id="bdb3f"></cite></p>

      <p id="bdb3f"><cite id="bdb3f"><th id="bdb3f"></th></cite></p><p id="bdb3f"></p>
        <p id="bdb3f"><cite id="bdb3f"></cite></p>

          <pre id="bdb3f"></pre>
          <pre id="bdb3f"><del id="bdb3f"><thead id="bdb3f"></thead></del></pre>

          <ruby id="bdb3f"><mark id="bdb3f"></mark></ruby><ruby id="bdb3f"></ruby>
          <pre id="bdb3f"><pre id="bdb3f"><mark id="bdb3f"></mark></pre></pre><output id="bdb3f"></output><p id="bdb3f"></p><p id="bdb3f"></p>

          <pre id="bdb3f"><del id="bdb3f"><progress id="bdb3f"></progress></del></pre>

                <ruby id="bdb3f"></ruby>

                **什么是數據庫三大范式** 1. 每一列都是不可分割的原子數據項 2. 實體的屬性完全依賴于主關鍵字 3. 任何非主屬性不依賴于其它非主屬性(在2NF基礎上消除傳遞依賴) **數據庫中設計中的常見問題** 1. 字段混在了一起 > ![](https://box.kancloud.cn/6a34335f77723f818ac576a25b7b8258_743x157.jpg) ![](https://box.kancloud.cn/831d7470be3e01aa6f22ab866803b6b5_881x136.jpg) 2. 數據表混在了一起 >![](https://box.kancloud.cn/05618151a1bcd4fa00c0e7339f593d14_661x349.jpg) 3. 不會處理表關系 > *一對一 (學生姓名, 學號)*? > *一對多 (老師, 學生)*? > *多對多 (學生, 課程)* **設計數據庫的小技巧** 1. 一個對象, 一張表 2. 一張表, 一個主鍵 3. 表名中有`數據庫名`做前綴 4. 字段名中有`表名`做前綴 5. 前綴后加`縮寫` 6. 數據表關系處理 **范式越高越好?** `新建數據庫指定編碼與排序規則` ``` create database `test2` default character set utf8 collate utf8_general_ci ```
                  <ruby id="bdb3f"></ruby>

                  <p id="bdb3f"><cite id="bdb3f"></cite></p>

                    <p id="bdb3f"><cite id="bdb3f"><th id="bdb3f"></th></cite></p><p id="bdb3f"></p>
                      <p id="bdb3f"><cite id="bdb3f"></cite></p>

                        <pre id="bdb3f"></pre>
                        <pre id="bdb3f"><del id="bdb3f"><thead id="bdb3f"></thead></del></pre>

                        <ruby id="bdb3f"><mark id="bdb3f"></mark></ruby><ruby id="bdb3f"></ruby>
                        <pre id="bdb3f"><pre id="bdb3f"><mark id="bdb3f"></mark></pre></pre><output id="bdb3f"></output><p id="bdb3f"></p><p id="bdb3f"></p>

                        <pre id="bdb3f"><del id="bdb3f"><progress id="bdb3f"></progress></del></pre>

                              <ruby id="bdb3f"></ruby>

                              哎呀哎呀视频在线观看