Part 3 Merging Databases

·       Merge Database A and Database B by cusip and year

use DatabaseB.dta,clear

merge 1:1 CUSIP8year using DatabaseA

Q3: [1 point] Report thefollowing

Number of Observations in Database A and not in B	“???”
Number of Observations in Database B and not in A	“???”
Matched Observations	“???”

·       Keep only matched.

keep if _merge==3

这是题目，之前做了两个database，请问part3 怎么做呢，stata菜鸟，麻烦一步一步指导

是不是要先打开之前做的两个database？但是打开后 输入 use DatabaseB.dta, clear

merge 1:1 CUSIP8 year using DatabaseA 就显示找不到database

请问怎么回事呢