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

STU_ID	STU_KEY	STU_CODE_1
123	2002123	A121
124	2002124	A122
125	2002125	A123
126	2002126	A124

–b table |STU_ID|STU_KEY|STU_CODE_2| |——|——-|———-| |123 |2002223|B121 | |124 |2002224|B122 | |125 |2002225|C123 | |126 |2002226|C124 | |127 |2002127|C125 |

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

-result data merge table

STU_ID	STU_KEY	STU_CODE_1	STU_CODE_2
123	2002123	A121
123	2002223		B121
124	2002124	A122
124	2002224		B122
125	2002125	A123
125	2002225		C123
126	2002126	A124
126	2002226		C124
127	2002127		C125

 '''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;