mybatis group by 分组查询

在MyBatis中，可以使用GROUP BY关键字进行分组查询。分组查询可以按照某个字段或多个字段中的值进行分组，相同值的记录会被归为一组。同时，可以使用聚合函数对每个分组进行统计计算。以下是几个示例：

1. 按照性别分组统计学生数量：
SELECT sex, COUNT(id) FROM student GROUP BY sex

2. 按照地址分组统计学生数量：
SELECT address, COUNT(id) FROM student GROUP BY address

3. 按照地址和性别分组统计学生数量：
SELECT address, sex, COUNT(id) FROM student GROUP BY address, sex

4. 按照地址和性别分组统计学生数量，并筛选出性别为1的结果：
SELECT address, sex, COUNT(id) FROM student GROUP BY address, sex HAVING sex = 1

在MyBatis中，可以使用XML配置文件或注解来编写以上查询语句，并通过调用相应的方法来执行查询操作。比如使用XML配置文件可以这样写：

<select id="groupQuery" resultType="java.util.HashMap">
SELECT sex, COUNT(id) FROM student GROUP BY sex
</select>

<select id="groupQuery" resultType="java.util.HashMap">
SELECT address, COUNT(id) FROM student GROUP BY address
</select>

<select id="groupQuery" resultType="java.util.HashMap">
SELECT address, sex, COUNT(id) FROM student GROUP BY address, sex
</select>

<select id="groupQuery" resultType="java.util.HashMap">
SELECT address, sex, COUNT(id) FROM student GROUP BY address, sex HAVING sex = 1
</select>

然后通过调用相应的方法来执行查询操作。例如，调用addressStudent方法来执行按地址分组统计学生数量的查询：

List<HashMap<String, Long>> addressStudent(); <span class="em">1</span><span class="em">2</span><span class="em">3</span>
#### 引用[.reference_title]
- *1* *2* *3* [Mybatis之分组查询](https://blog.csdn.net/leijie0322/article/details/124103798)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v93^chatsearchT3_1"}}] [.reference_item style="max-width: 100%"]
[ .reference_list ]