如何使用 Sqlite3 用列表中的值更新整个列 [英] How to update entire column with values in list using Sqlite3

问题描述

我有一个本地存储在 sqlite3 数据库中的数据集.我提取了一列，执行了一些操作，现在想要替换数据库列中的所有值.我该怎么做?

列的长度和列表的长度保证相同.我只想用新值更新表.有没有一种简单的方法可以一次性完成这一切?

使用 python 2.7

编辑添加:

myList 是一个 Pandas 系列，由 dtype 'object' 的 numpy 数组支持.表格列 myCol 是文本格式.

In [1]: curr.execute('UPDATE test SET myCol= ?', myList)---------------------------------------------------------------------------ProgrammingError Traceback(最近一次调用最后一次)f:\python\在 <module>()---->1 curr.execute('UPDATE test SET myCol = ?', myList)ProgrammingError: 提供的绑定数量不正确.当前语句使用 1，并且提供了 401125.

解决方案

使用 .executemany() 方法:

curr.executemany('UPDATE test SET myCol= ?', myList)

然而，myList 必须在这里是一个元组序列.如果不是，生成器表达式将创建这些元组:

curr.executemany('UPDATE test SET myCol= ?', ((val,) for val in myList))

演示(带插入):

<预><代码>>>>导入 sqlite3>>>conn=sqlite3.connect(':memory:')>>>conn.execute('创建表测试(myCol)')<sqlite3.Cursor 对象在 0x10542f1f0>>>>conn.commit()>>>myList = ('foo', 'bar', '垃圾邮件')>>>conn.executemany('INSERT into test values (?)', ((val,) for val in myList))<sqlite3.Cursor 对象在 0x10542f180>>>>list(conn.execute('select * from test'))[(u'foo',), (u'bar',), (u'spam',)]

请注意，对于 UPDATE 语句，您必须有一个 WHERE 语句来标识哪一行更新.没有 WHERE 过滤器的 UPDATE 将更新所有行.

确保您的数据有一个行标识符；在这种情况下，使用命名参数可能更容易:

my_data = ({id=1, value='foo'}, {id=2, value='bar'})cursor.executemany('UPDATE test SET myCol=:value WHERE rowId=:id', my_data)

I have a dataset stored locally in an sqlite3 database. I extracted a column, performed some operations and now want to replace ALL of the values in the database column. How can I do this?

The length of the column and the list are guaranteed to be the same length. I simply want to update the table with the new values. Is there an easy way to do this all at once?

Using python 2.7

Edited to add:

myList is a pandas series backed by a numpy array of dtype 'object'. The table column, myCol is text formatted.

In [1]: curr.execute('UPDATE test SET myCol= ?', myList)

---------------------------------------------------------------------------
ProgrammingError                          Traceback (most recent call last)
f:\python\<ipython-input-52-ea41c426502a> in <module>()
----> 1 curr.execute('UPDATE test SET myCol = ?', myList)

ProgrammingError: Incorrect number of bindings supplied. The current statement uses 1, and there are 401125 supplied.

解决方案

Use the .executemany() method instead:

curr.executemany('UPDATE test SET myCol= ?', myList)

However, myList must be a sequence of tuples here. If it is not, a generator expression will do to create these tuples:

curr.executemany('UPDATE test SET myCol= ?', ((val,) for val in myList))

Demonstration (with insertions):

>>> import sqlite3
>>> conn=sqlite3.connect(':memory:')
>>> conn.execute('CREATE TABLE test (myCol)')
<sqlite3.Cursor object at 0x10542f1f0>
>>> conn.commit()
>>> myList = ('foo', 'bar', 'spam')
>>> conn.executemany('INSERT into test values (?)', ((val,) for val in myList))
<sqlite3.Cursor object at 0x10542f180>
>>> list(conn.execute('select * from test'))
[(u'foo',), (u'bar',), (u'spam',)]

Note that for an UPDATE statement, you have to have a WHERE statement to identify what row to update. An UPDATE without a WHERE filter will update all rows.

Make sure your data has a row identifier to go with it; in this case it may be easier to use named parameters instead:

my_data = ({id=1, value='foo'}, {id=2, value='bar'})
cursor.executemany('UPDATE test SET myCol=:value WHERE rowId=:id', my_data)

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