关于postgresql：PGError：错误：列“p.name”必须出现在GROUP BY子句中或用于聚合函数

PGError: ERROR: column “p.name” must appear in the GROUP BY clause or be used in an aggregate function

我的查询出错了。为什么？我不明白:(

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SELECT p.name, p.id, SUM(hours) AS hours, SUM(logged_hours) AS logged_hours
FROM (
SELECT project_id, DATE, hours, NULL AS logged_hours
FROM #{ScheduleEntry.table_name}
WHERE user_id = #{USER.current.id}
AND DATE BETWEEN '%s' AND '%s'
UNION
SELECT project_id, spent_on AS DATE, NULL AS hours, SUM(#{TimeEntry.table_name}.hours) AS logged_hours
FROM #{TimeEntry.table_name}
WHERE user_id = #{USER.current.id}
AND spent_on BETWEEN '%s' AND '%s'
GROUP BY project_id, DATE
) AS results
LEFT JOIN #{Project.table_name} AS p ON p.id = results.project_id
GROUP BY project_id