sql中groupby的用法
时间: 2023-09-03 18:14:29 浏览: 55
在SQL中,GROUP BY用于将数据集按照指定的列进行分组,并允许对每个分组进行聚合操作。在使用GROUP BY时,需要注意以下几点:
1. 在GROUP BY子句中不能使用SELECT子句中定义的列的别名。这是因为GROUP BY子句的执行优先级高于SELECT子句,所以如果在SELECT中使用了列的别名,GROUP BY子句无法识别。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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