如何比较2个列表并将它们合并到Python/MySQL中？

Question

我想合并数据。以下是我的MySQL表。我想用Python遍历这两个列表（其中一个用dupe ='x'，另一个用null dupes）。

这是示例数据。实际数据是巨大的。

例如：

a b c d e f key dupe 
-------------------- 
1 d c f k l 1 x 
2 g h j 1  
3 i h u u 2 
4 u r  t 2 x 

从上面的示例表，所需的输出是：

a b c d e f key dupe 
-------------------- 
2 g c h k j 1 
3 i r h u u 2 

我到目前为止有：

import string, os, sys 
import MySQLdb 
from EncryptedFile import EncryptedFile 

enc = EncryptedFile(os.getenv("HOME") + '/.py-encrypted-file') 
user = enc.getValue("user") 
pw = enc.getValue("pw") 

db = MySQLdb.connect(host="127.0.0.1", user=user, passwd=pw,db=user) 

cursor = db.cursor() 
cursor2 = db.cursor() 

cursor.execute("select * from delThisTable where dupe is null") 
cursor2.execute("select * from delThisTable where dupe is not null") 
result = cursor.fetchall() 
result2 = cursor2.fetchall() 

for each record 
    for each field 
     perform the comparison and perform the necessary updates 

      ### How do I compare the record with same key value and update the original row null field value with the non-null value from the duplicate? Please fill this void... 


cursor.close() 
cursor2.close() 
db.close() 

谢谢你们！

Answer 1

OK，让我们有一些有趣的...

mysql> create table so (a int, b char, c char, d char, e char, f char, `key` int, dupe char); 
Query OK, 0 rows affected (0.05 sec) 

mysql> insert into so values (1, 'd', 'c', 'f', 'k', 'l', 1, 'x'), (2, 'g', null, 'h', null, 'j', 1, null), (3, 'i', null, 'h', 'u', 'u', 2, null), (4, 'u', 'r', null, null, 't', 2, 'x'); 
Query OK, 4 rows affected (0.00 sec) 
Records: 4 Duplicates: 0 Warnings: 0 

mysql> select * from so order by a; 
+------+------+------+------+------+------+------+------+ 
| a | b | c | d | e | f | key | dupe | 
+------+------+------+------+------+------+------+------+ 
| 1 | d | c | f | k | l | 1 | x | 
| 2 | g | NULL | h | NULL | j | 1 | NULL | 
| 3 | i | NULL | h | u | u | 2 | NULL | 
| 4 | u | r | NULL | NULL | t | 2 | x | 
+------+------+------+------+------+------+------+------+ 
4 rows in set (0.00 sec) 

---

Python 2.6.5 (r265:79063, Mar 26 2010, 22:43:05) 
[GCC 4.2.1 (Apple Inc. build 5646) (dot 1)] on darwin 
Type "help", "copyright", "credits" or "license" for more information. 
>>> import MySQLdb 
>>> db = MySQLdb.connect(host="127.0.0.1", db="test") 
>>> c = db.cursor() 
>>> c.execute("SELECT a, b, c, d, e, f, `key`, dupe FROM so") 
4L 
>>> rows = c.fetchall() 
>>> rows 
((1L, 'd', 'c', 'f', 'k', 'l', 1L, 'x'), (4L, 'u', 'r', None, None, 't', 2L, 'x'), (2L, 'g', None, 'h', None, 'j', 1L, None), (3L, 'i', None, 'h', 'u', 'u', 2L, None)) 
>>> data = dict() 
>>> for row in rows: 
... key, isDupe = row[-2], row[-1] 
... if key not in data: 
... data[key] = list(row[:-1]) 
... else: 
... for i in range(len(row)-1): 
... if data[key][i] is None or (not isDupe and row[i] is not None): 
...  data[key][i] = row[i] 
... 
>>> data 
{1L: [2L, 'g', 'c', 'h', 'k', 'j', 1L], 2L: [3L, 'i', 'r', 'h', 'u', 'u', 2L]}