项目场景：

需要查询同时拥有某产品的用户信息

需求：

某业务需要提供根据产品查询拥有产品的用户信息（产品可能为多个）

解决方案：

1. group by + having

        SELECT su.user_code, u.user_name,su.role_code,r.role_name data_code FROM sys_user_data_auth su
        JOIN sys_user u ON su.user_code = u.user_code AND u.delete_flag = 0
        JOIN sys_role r ON su.role_code = r.role_code AND r.delete_flag = 0
        WHERE su.delete_flag = 0 
        AND su.data_code IN
        <foreach collection="dataCodeList" item="item" open="(" separator="," close=")">
            #{item}
        </foreach>
        AND su.role_code = #{roleCode}
        GROUP BY su.user_code,su.role_code
        HAVING count(*) = ${dataCodeList.size()}

注:使用#{}获取数字进行比较时会报错，故使用${}引用
2. EXISTS