Copy info from one table two another with conditions

I am importing a csv file into a temp table (works fine), now I want to take the data in the temp table based off of the temp id compared to the id of the permanant file.

basically if the record id exists skip to the next line and so forth, I am able to import everything just fine but I cannot get the WHERE condition to acually work.

INSERT INTO TABLE2 (COL1, COL2, COL3) SELECT COL1, COL4, COL7 FROM TABLE1 WHERE table2.col1 <> table1.col1

this is what my actual code is

INSERT INTO USER_INFO (fpu_id,FIRSTNAME, LASTNAME, BOXNUMBER) SELECT id,first,last,box FROM stmailbox WHERE stmailbox.id <> dbo.USER_INFO.USERID

this is the actual error that I get.

Server: Msg 107, Level 16, State 3, Line 2
The column prefix 'USER_INFO' does not match with a table name or alias name used in the query.

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thanks for the helpWell I think that I got it...

INSERT INTO USER_INFO (id,FIRSTNAME, LASTNAME, BOXNUMBER) SELECT id,first,last,box FROM stmailbox WHERE stmailbox.id NOT IN (SELECT id FROM USER_INFO)

Let me know if there is a better way

Thanks