求助，多表关联更新问题

Linux521

目前有三个表A(uacct,user_name),B(uid,username),C(uid,realname);

A.user_uacct=B.username

B.uid=C.uid

想取出A.user_name更新到C.realname. 如何写出批量更新的SQL呢，谢谢。

seesea2517

回复 1# Linux521
试一下：

1. mysql> select * from A;
   
2. +-------+-----------+
   
3. | uacct | user_name |
   
4. +-------+-----------+
   
5. | aaa   | axx       |
   
6. | bbb   | bxx       |
   
7. | ccc   | cxx       |
   
8. +-------+-----------+
   
9. 3 rows in set
   
10. 
    
11. mysql> select * from B;
    
12. +-----+-----------+
    
13. | uid | user_name |
    
14. +-----+-----------+
    
15. | 1   | aaa       |
    
16. | 2   | bbb       |
    
17. | 3   | ccc       |
    
18. +-----+-----------+
    
19. 3 rows in set
    
20. 
    
21. mysql> select * from C
    
22. ;
    
23. +-----+----------+
    
24. | uid | realname |
    
25. +-----+----------+
    
26. | aaa | NULL     |
    
27. | bbb | NULL     |
    
28. | ccc | NULL     |
    
29. +-----+----------+
    
30. 3 rows in set
    
31. 
    
32. mysql> update A, B, C set realname = A.user_name where A.uacct = B.user_name and B.uid = C.uid;
    
33. Query OK, 3 rows affected
    
34. Rows matched: 3  Changed: 3  Warnings: 0
    
35. mysql> select * from C;
    
36. +-----+----------+
    
37. | uid | realname |
    
38. +-----+----------+
    
39. | 1   | axx      |
    
40. | 2   | bxx      |
    
41. | 3   | cxx      |
    
42. +-----+----------+
    
43. 3 rows in set
    
44. 
    
45. mysql>

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will009

回复 2# seesea2517
不对吧，你的例子中B.uid=C.uid吗

seesea2517

回复 3# will009
感谢指出，那是最初的输出，后来测试发现做错测试数据了，改完后直接测试没重新输出截图了，这是改下后的 uid 数据：

1. ysql> select * from B;
   
2. +-----+-----------+
   
3. | uid | user_name |
   
4. +-----+-----------+
   
5. | 1   | aaa       |
   
6. | 2   | bbb       |
   
7. | 3   | ccc       |
   
8. +-----+-----------+
   
9. 3 rows in set
   
10. 
    
11. mysql> select * from C
    
12. ;
    
13. +-----+----------+
    
14. | uid | realname |
    
15. +-----+----------+
    
16. | 1   | axx      |
    
17. | 2   | bxx      |
    
18. | 3   | cxx      |
    
19. +-----+----------+
    
20. 3 rows in set
    

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Linux521

感谢 seesea2517 will009   。已解决，当时想多了点