How to merge two tables using SAS proc sql

Here is the exam data table that I would like to process here:

-origin data

–a table

–b table STU_IDSTU_KEYSTU_CODE_2 ————-———- 123 2002223B121 124 2002224B122 125 2002225C123 126 2002226C124 127 2002127C125

I want to merge between ‘a’ and ‘b’ tables using code of SAS proc sql as follows.

-result data merge table

 '''error code'''
 PROC SQL;
 CREATE TABLE a_b_merge as
 SELECT t1.STU_ID, 
        t1.STU_KEY, 
        t1.STU_CODE_1
        t2.STU_CODE_2
 FROM a as t1 full join b as t2
 ON t1.STU_ID=t2.STU_ID
 QUIT;  

Let me know how to solve this problem.