update t1 set t1.a02=t2.b02 from a t1,b t2 where t1.a01=t2.b02

------解决方案--------------------
探讨

SQL code

update t1 set t1.a02=t2.b02 from a t1,b t2 where t1.a01=t2.b02


------解决方案--------------------
C# code

DROP TABLE A
DROP TABLE B
CREATE TABLE A
(
  a01  INT,
  a02  VARCHAR(10)  

)
INSERT INTO A
    
SELECT 1,'haha'    UNION ALL
SELECT 2,'gaga'   UNION ALL
SELECT 3,'jiji' 

CREATE TABLE B 
(
  b01  INT,
  b02  VARCHAR(10)  

)
INSERT INTO B
    
SELECT 1,'cc'    UNION ALL
SELECT 2,'dd'

SELECT * FROM A 
SELECT * FROM B 

UPDATE A SET A.a02=B.b02 FROM A,B WHERE B.b01=A.a01
SELECT * FROM A
/*
a01         a02        
----------- ---------- 
1           cc
2           dd
3           jiji

（所影响的行数为 3 行）
*/