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解释第一范式（1NF）
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#IAJL22
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2024-08-13 10:11
<p>解释第一范式（1NF）的定义，并给出一个转换为1NF的实例。</p><br><p>第一范式（1NF）要求表中的每个字段必须只有单一的（不可分的）值，即字段不能包含多个值或重复的组合。</p> <p>非1NF示例：</p> <pre><code class="language-sql">CREATE TABLE Students ( StudentID int, Name varchar(255), PhoneNumbers varchar(255) -- 这里违反了1NF，因为一个字段中有多个电话号码 );</code></pre> <p>转换为1NF的版本：</p> <pre><code class="language-sql">CREATE TABLE Students ( StudentID int, Name varchar(255) ); CREATE TABLE PhoneNumbers ( StudentID int, PhoneNumber varchar(255) );</code></pre>
<p>解释第一范式（1NF）的定义，并给出一个转换为1NF的实例。</p><br><p>第一范式（1NF）要求表中的每个字段必须只有单一的（不可分的）值，即字段不能包含多个值或重复的组合。</p> <p>非1NF示例：</p> <pre><code class="language-sql">CREATE TABLE Students ( StudentID int, Name varchar(255), PhoneNumbers varchar(255) -- 这里违反了1NF，因为一个字段中有多个电话号码 );</code></pre> <p>转换为1NF的版本：</p> <pre><code class="language-sql">CREATE TABLE Students ( StudentID int, Name varchar(255) ); CREATE TABLE PhoneNumbers ( StudentID int, PhoneNumber varchar(255) );</code></pre>
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