遍历python中mysql中的行

Question

I have a mysql database table consisting of 8 columns as given

ID   C1    C2    C3    C4    C5    C6    C7 

1    25    33    76    87    56    76    47
2    67    94    90    56    77    32    84
3    53    66    24    93    33    88    99
4    73    34    52    85    67    82    77
5    78    55    52   100    78    68    32
6    67    35    60    93    88    53    66

I need to fetch 3 rows of all the column except the ID column at a time. So far I did this code in python which fetches me the rows with ID values 1,2,3.

ex = MySQLdb.connect(host,port,user,passwd,db)
with ex:
 ex_cur = ex.cursor()
 ex.execute("SELECT C1,C2,C3,C4,C5,C6,C7 FROM table LIMIT 0, 3;") 

In the second cycle I need to fetch rows with ID values 2,3,4, third cycle fetches rows with ID values 3,4,5 which should continue till the end of the database. What query should I use to iterate through the table so as to get the desired set of rows.

Answer 1

I believe there are three ways of doing this: (I'm going to explain at a very high level)

1. You can create a queue with a size limit of 3 and read in the rows as a stream. Once the queue reaches the max size of 3, do your processing, pop off the first element in your queue, and proceed with the stream. (More efficient)

2. You would need an iterator and reset your cursor for every set of 3 IDs that you have to do.

3. Since your table is relatively small (would not suggest this for larger tables), load the whole database into a data structure/into memory. Perhaps make an object for the rows and use an ORM to map rows to objects. Then you would simply have to iterate through each object, or set of 3 objects, and do the necessary processing.