Question

我在Jupyter笔记本中使用sql包，我理解如何在查询中使用变量：

client = "Disney"
queryid = %sql SELECT * FROM mytable WHERE name = :client

我不明白的是如何将列表传递给我的查询，例如：

clients = ["Disney", "Netflix", "Sky"]
queryid = %sql SELECT * FROM mytable WHERE name in (:clients)

这会引发一个错误，指出我的SQL错误。在此设置中处理列表的方法是什么？

Answer 1

使用sqlite3的演示案例：

In [1]: import sqlite3
In [2]: conn = sqlite3.connect('example.db')
In [3]: c = conn.cursor()
In [4]: c.execute('''CREATE TABLE stocks
   ...:              (date text, trans text, symbol text, qty real, price real)''')
   ...: 
   ...: # Insert a row of data
   ...: c.execute("INSERT INTO stocks VALUES ('2006-01-05','BUY','RHAT',100,35.1
   ...: 4)")
   ...: 
   ...: # Save (commit) the changes
   ...: conn.commit()
   ...: 
In [5]: # Larger example that inserts many records at a time
   ...: purchases = [('2006-03-28', 'BUY', 'IBM', 1000, 45.00),
   ...:              ('2006-04-05', 'BUY', 'MSFT', 1000, 72.00),
   ...:              ('2006-04-06', 'SELL', 'IBM', 500, 53.00),
   ...:             ]
   ...: c.executemany('INSERT INTO stocks VALUES (?,?,?,?,?)', purchases)

我可以使用以下命令获取与多个字符串匹配的值：

In [31]: c.execute('SELECT * FROM stocks WHERE symbol IN (?,?)',('IBM','RHAT'))
Out[31]: <sqlite3.Cursor at 0xaf703fa0>
In [32]: c.fetchall()
Out[32]: 
[('2006-01-05', 'BUY', 'RHAT', 100.0, 35.14),
 ('2006-03-28', 'BUY', 'IBM', 1000.0, 45.0),
 ('2006-04-06', 'SELL', 'IBM', 500.0, 53.0)]

或使用Parameter substitution for a SQLite "IN" clause

中的通用解决方案

In [33]: alist=['RHAT','IBM']
In [34]: c.execute('SELECT * FROM stocks WHERE symbol IN (%s)' %
    ...:                            ','.join('?'*len(alist)), 
    ...:                            alist)
    ...:                            
Out[34]: <sqlite3.Cursor at 0xaf703fa0>
In [35]: c.fetchall()
Out[35]: 
[('2006-01-05', 'BUY', 'RHAT', 100.0, 35.14),
 ('2006-03-28', 'BUY', 'IBM', 1000.0, 45.0),
 ('2006-04-06', 'SELL', 'IBM', 500.0, 53.0)]

c.execute('SELECT * FROM stocks WHERE symbol IN (:1,:2)',alist)，可能还有其他形式。

另见：

sqlite3 "IN" clause

我认为MYSQL和%sql iterface的行为相同;但是我没有安装那些。

使用正确的引文文字也可以（再次sqlite3）

c.execute('SELECT * FROM stocks WHERE symbol IN ("IBM","RHAT")')

或

In [80]: 'SELECT * FROM stocks WHERE symbol IN (%s)'%','.join('"%s"'%x for x in alist)
Out[80]: 'SELECT * FROM stocks WHERE symbol IN ("RHAT","IBM")'
In [81]: c.execute(_)

所以我猜测：

%sql SELECT * FROM stocks WHERE symbol IN ("IBM","RHAT")

即使某种形式的(:....)没有，

也能正常工作。

我安装了%sql

In [5]: %%sql
   ...: sqlite:///example.db
   ...: 

Out[5]: 'Connected: None@example.db'
In [7]: %sql SELECT * from stocks
Done.
Out[7]: 
[('2006-01-05', 'BUY', 'RHAT', 100.0, 35.14),
 ('2006-03-28', 'BUY', 'IBM', 1000.0, 45.0),
 ('2006-04-05', 'BUY', 'MSFT', 1000.0, 72.0),
 ('2006-04-06', 'SELL', 'IBM', 500.0, 53.0)]

In [9]: %sql SELECT * from stocks where symbol in ('IBM')
Done.
Out[9]: 
[('2006-03-28', 'BUY', 'IBM', 1000.0, 45.0),
 ('2006-04-06', 'SELL', 'IBM', 500.0, 53.0)]

In [10]: %sql SELECT * from stocks where symbol in ('IBM','RHAT')
Done.
Out[10]: 
[('2006-01-05', 'BUY', 'RHAT', 100.0, 35.14),
 ('2006-03-28', 'BUY', 'IBM', 1000.0, 45.0),
 ('2006-04-06', 'SELL', 'IBM', 500.0, 53.0)]

字符串格式化方法有效：

In [11]: alist=['RHAT','IBM']
In [12]: cmd='SELECT * FROM stocks WHERE symbol IN (%s)'%','.join('"%s"'%x for x
    ...:  in alist)
In [13]: cmd
Out[13]: 'SELECT * FROM stocks WHERE symbol IN ("RHAT","IBM")'
In [14]: %sql $cmd
Done.
Out[14]: 
[('2006-01-05', 'BUY', 'RHAT', 100.0, 35.14),
 ('2006-03-28', 'BUY', 'IBM', 1000.0, 45.0),
 ('2006-04-06', 'SELL', 'IBM', 500.0, 53.0)]

:语法没有详细记录。目前还不清楚谁在实施它。（$是标准的Ipython变量替换）。

In [18]: sym='IBM'
In [19]: %sql SELECT * from stocks where symbol in (:sym)
Done.
Out[19]: 
[('2006-03-28', 'BUY', 'IBM', 1000.0, 45.0),
 ('2006-04-06', 'SELL', 'IBM', 500.0, 53.0)]

symbol in (:sym1,:sym2)有效

到目前为止，我还没有看到%sql使用传统SQL占位符语法的证据。

看起来您（？）提交并关闭了github上的问题，https://github.com/catherinedevlin/ipython-sql/issues/92

使该解决方案适用于引用字符串：

In [74]: mystring = '({})'.format(','.join('"{}"'.format(e) for e in alist))
In [75]: mystring
Out[75]: '("RHAT","IBM")'
In [76]: %sql SELECT * from stocks where symbol in $mystring
Done.

换句话说，使用ipython $注入而不是:表单。

查看ipython-sql源代码：

ipython-sql/blob/master/src/sql/run.py
def run(conn, sql, config, user_namespace):
    ...
    txt = sqlalchemy.sql.text(statement)
    result = conn.session.execute(txt, user_namespace)

看起来:name语法是sqlalchemy绑定参数，并由sqlalchemy.sql.text和sqlalchemy.sql.bindparam处理

（http://docs.sqlalchemy.org/en/latest/orm/tutorial.html#orm-tutorial-literal-sql）

此错误表示每个绑定参数都已转换为?占位符，以及匹配的parameters条目：

In [96]: %sql SELECT * from stocks where symbol in :mystring
(sqlite3.OperationalError) near "?": syntax error [SQL: 'SELECT * from stocks where symbol in ?'] [parameters: ('("RHAT","IBM")',)]

因此，我生成IN (?,?,...)以匹配列表长度的原始解决方案是正确的SQL，即使它不适用于sqlalchemy和%sql。

Answer 2

关于在SQL查询中将$与python元组一起应用的轶事：

它需要在％sql行中使用，不能*在%% sql代码块中使用。使用行连续反斜杠可以提高查询的可读性。

*据我所知

Answer 3

删除括号对我有用。

clients = ["Disney", "Netflix", "Sky"]
queryid = %sql SELECT * FROM mytable WHERE name in :clients

Answer 4

此功能使我免于此类问题的困扰：


> def splitParam(param): # this function splits multiple values of filter
    filteredParam = ""
    if param:
        for item in param:
            if filteredParam=="":
                filteredParam += "'" + item.upper() + "'"
            else:
                filteredParam += ", '" + item.upper() + "'"

    return filteredParam

如何在％sql查询

4 个答案: