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<span id="id1"></span><h1>DECRBY<a class="headerlink" href="#decrby" title="Permalink to this headline">¶</a></h1>
<p><strong>DECRBY key decrement</strong></p>
<p>将 <code class="docutils literal"><span class="pre">key</span></code> 所储存的值减去减量 <code class="docutils literal"><span class="pre">decrement</span></code> 。</p>
<p>如果 <code class="docutils literal"><span class="pre">key</span></code> 不存在，那么 <code class="docutils literal"><span class="pre">key</span></code> 的值会先被初始化为 <code class="docutils literal"><span class="pre">0</span></code> ，然后再执行 <a class="reference internal" href="#decrby">DECRBY</a> 操作。</p>
<p>如果值包含错误的类型，或字符串类型的值不能表示为数字，那么返回一个错误。</p>
<p>本操作的值限制在 64 位(bit)有符号数字表示之内。</p>
<p>关于更多递增(increment) / 递减(decrement)操作的更多信息，请参见 <a class="reference internal" href="incr.html#incr"><span>INCR</span></a> 命令。</p>
<dl class="docutils">
<dt><strong>可用版本：</strong></dt>
<dd>>= 1.0.0</dd>
<dt><strong>时间复杂度：</strong></dt>
<dd>O(1)</dd>
<dt><strong>返回值：</strong></dt>
<dd>减去 <code class="docutils literal"><span class="pre">decrement</span></code> 之后， <code class="docutils literal"><span class="pre">key</span></code> 的值。</dd>
</dl>
<div class="highlight-python"><div class="highlight"><pre># 对已存在的 key 进行 DECRBY
redis> SET count 100
OK
redis> DECRBY count 20
(integer) 80
# 对不存在的 key 进行DECRBY
redis> EXISTS pages
(integer) 0
redis> DECRBY pages 10
(integer) -10
</pre></div>
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