Description error detail
My file: http://www.mediafire.com/?g09b648dhv5q9ii
Run file , Select Hóa Đơn

Choose DaTH,

Type info, It will have problem below
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I tryed to fix:
Select Table T_HangHoa

Changge Indexed from Yes to No but can't, error
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I try to delete primary key, but can't

Please advices