mysql查询结果合并去重、合并全部

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<span style="font-family: Arial, Helvetica, sans-serif;">SELECT doctor_id,doctor_name,doctor_position,COUNT(*) amount</span>

FROM((SELECT d.doctor_id,d.doctor_name,d.doctor_positionFROM doctor_info d LEFT JOIN hospitalized h ON d.doctor_id=h.doctor_id)UNION ALL(SELECT d.doctor_id,d.doctor_name,d.doctor_positionFROM doctor_info d LEFT JOIN u_outpatient o ON o.doctor_id = d.doctor_id)UNION ALL(SELECT d.doctor_id,d.doctor_name,d.doctor_positionFROM doctor_info d LEFT JOIN med_follow f ON f.doctor_id = d.doctor_id)) ddGROUP BY doctor_nameORDER BY amount DESC

合并全部

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合并去重

(SELECT d.doctor_id,d.doctor_name,d.doctor_positionFROM doctor_info d LEFT JOIN hospitalized h ON d.doctor_id=h.doctor_id)UNION(SELECT d.doctor_id,d.doctor_name,d.doctor_positionFROM doctor_info d LEFT JOIN u_outpatient o ON o.doctor_id = d.doctor_id)UNION(SELECT d.doctor_id,d.doctor_name,d.doctor_positionFROM doctor_info d LEFT JOIN med_follow f ON f.doctor_id = d.doctor_id)

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