Question

我需要一次从我的sqlite3数据库中检索160行的结果，然后重复一遍，直到我的查询没有剩下的行，这就是我所拥有的：

conn = sqlite3.connect("C:\\Users\\%s\\AppData\\Roaming\\GridcoinResearch\\reports\\Rain.db" % user_account)
c = conn.cursor()
conn.text_factory = str
address = c.execute('select Address from NNDATA where NeuralMagnitude != 0 and NeuralMagnitude is not null and CPID in (select cpids from GRIDCOINTEAM)').fetchmany(160)
conn.text_factory = float
nn_mag = c.execute('select NeuralMagnitude from NNDATA where NeuralMagnitude != 0 and NeuralMagnitude is not null and CPID in (select cpids from GRIDCOINTEAM)').fetchmany(160)
conn.close()

while True:
    if nn_mag == ():
        sys.exit("Complete")

sys.exit的原因是我在conn.close()和while True:之间有许多其他代码，所以当最后一个循环完成后，我可以退出程序。现在它正在进行第一次传递，然后cmd.exe挂起。

编辑：刚刚重新启动我不告诉循环选择NEXT 160，哦亲爱的！

Answer 1

如果没有项目左侧，fetchmany属性将返回一个空列表，因此您只需检查其结果的验证。另请注意，您应从查询和limit中删除fetchall。因为使用fetchmany的全部本质是从游标对象获取有限的结果。

chunk_size = 160
while True:
    result = nn_mag.fetchmany(chunk_size)
    if not result:
        sys.exit("Complete")
    else:
         # do something with result

Answer 2

好的答案是：

conn = sqlite3.connect("C:\\Users\\%s\\AppData\\Roaming\\GridcoinResearch\\reports\\Rain.db" % user_account)
    c = conn.cursor()
    position = 00
    while True:
        conn.text_factory = str
        address_db = c.execute('select Address from NNDATA where NeuralMagnitude != 0 and NeuralMagnitude is not null and CPID in (select cpids from GRIDCOINTEAM) limit {}, 160'.format(position)).fetchall()
        conn.text_factory = float
        rac_db = c.execute('select rac from GRIDCOINTEAM where rac != 0 and rac is not null limit {}, 160'.format(position)).fetchall()
        if not address_db:
            conn.close()
            sys.exit("Complete")
        else:
            position += 160

sqlite上的python循环选择.fetchmany（）直到没有条目

2 个答案: