econfj 发表于 2011-6-1 21:35
(note: you are using old merge syntax; see [R] merge for new syntax)
variables deal_no xadv_code do not uniquely identify observations in the master data
variables deal_no xadv_code do not uniquely identify observations in 04acq_loyalty.dta

事实上，我试过下面的语句，
use 07acqswitch.dta,clear
bysort deal_no xadv_code:gen y=_n
发现出来的出来的y都是1，这足以证明deal_no xadv_code能uniquely identify observations。但是为什么会有上面的出错信息？

econfj 发表于 2011-6-1 21:35 用的是stata11
. use 07acqswitch.dta,clear
. sort deal_no xadv_code
. merge deal_no xadv_code using 04acq_loyalty.dta
(note: you are using old merge syntax; see [R] merge for new syntax)
variables deal_no xadv_code do not uniquely identify observations in the master data
variables deal_no xadv_code do not uniquely identify observations in 04acq_loyalty.dta