use "C:\Users\23290\Desktop\自然灾害.dta", clear

. merge 1:m year province using 投资全.dta
variable V3 is double in master but strL in using data
    You could specify merge's force option to ignore this
    string/numeric mismatch.  The using variable would then be
    treated as if it contained "".
r(106);

.
. drop if _merge!=3
_merge not found
r(111);

.
. drop _merge
variable _merge not found
r(111);

上面那个是什么意思啊，哪里出错了呢