rename Stkcd cd

. rename reptdt year

. save "D:\stata14教学-\董高.dta", replace
file D:\stata14教学-\董高.dta saved

. use "D:\stata14教学-\董任.dta"

. rename Stkcd cd

. rename reptdt year

. save "D:\stata14教学-\董任.dta", replace
file D:\stata14教学-\董任.dta saved

. merge 1:1 cd year personid using 董高.dta
variables cd year personid do not uniquely identify observations in the master data
r(459);

请问我该怎么合并数据啊，为啥它会合并不成功