“ UNION”行動的排序規則的非法混合

Question

 SELECT a.paid, a.total, a.remain, a.date, a.patient_id FROM (
(SELECT paid, total, remain, date, patient_id FROM payment ) 
UNION 
(SELECT paid, total_need AS total, remain, date, patient_id FROM patient_vouchers ) 
 ) a
 WHERE a.patient_id ='.$patient_id.'
ORDER BY a.date ASC

我需要按日期從兩個不同的表中獲取記錄，所以在此sql語句中有什么問題讓我得到該錯誤？

Answer 1

查找具有不同排序規則的變量並對齊它們，例如使用COLLATE utf8_general_ci