如何使用 pysqlite 更新 SQLite 中的列，我首先需要从表中的其他数据获取条件值? [英] How to update a column in SQLite using pysqlite where I first needed to obtain a conditional value from other data in my table?

问题描述

因此，我在更新数据库时遇到以下问题:

So, I have the following issue when updating my database:

我的表格中有一个列，我需要将其分成三部分，因此我有以下代码:

I have a column in my table that I need to split in three essentially and so I have the following code:

with con:
  cur = con.cursor()
  cur.execute('SELECT Column1 FROM MainTable')
  while True row = cur.fetchone() 
    if row == None:
      break 
for line in row: a, b, c= line.split('-') 
  print (b);

例如，它给了我第二列的值.但是，我需要使用这些值更新第二列，为此我尝试在底部添加以下内容:

which gives me the values of the second column for instance. However, I need to UPDATE that second column with those values and for this I have tried adding the following at the bottom:

cur.execute('UPDATE MainTable SET Col_2 = ?' WHERE Id = 1, (row, Id))

con.commit()

但是，由于某种原因，这运行得不好.

However, for some reason this isn't running well.

推荐答案

要更新特定行，您需要一种方法来标识该行.您似乎有一个ID"列，因此请与您要拆分的字符串一起阅读.

To update a specific row, you need a way to identify the row. You appear to have an "ID" column, so read that together with the string you want split.

SQL 语句与 Python 无关；您在 Python 中所做的是构造一个 SQL 字符串，然后将其提供给数据库以执行.(使用 ? 样式的参数可以避免字符串格式问题和 SQL 注入攻击；始终将它们用于值.)

SQL statements have nothing to do with Python; what you do in Python is to construct an SQL string that you then give to the database to execute. (Using ?-style parameters avoids string formatting problems and SQL injection attacks; always use them for values.)

cur.execute('SELECT ID, Column1 FROM MainTable')
for id, col1 in cur.fetchall():
    a, b, c = col1.split('-')
    cur.execute('UPDATE MainTable SET ColA = ?, ColB = ?, ColC = ? WHERE ID = ?',
                [a, b, c, id])
con.commit()

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