如何比较 2 个列表并在 Python/MySQL 中合并它们？

Question

我想合并数据。以下是我的 MySQL 表。我想使用 Python 遍历两个列表的列表（一个带有 dupe = 'x' 和另一个带有 null dupes）。

这是示例数据。实际数据非常庞大。

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

从上面的示例表中，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

到目前为止我所拥有的：

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()

谢谢大家！

Answer 1

好吧，让我们玩得开心……

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]}