如何在 pyodbc 中使用 executemany 运行多个 SELECT 查询答案

【问题标题】：How to use executemany in pyodbc to run multiple SELECT queries如何在 pyodbc 中使用 executemany 运行多个 SELECT 查询
【发布时间】：2020-09-27 10:59:22
【问题描述】：

我使用 PYODBC 根据 pandas 数据框列的值多次查询 SQL DB（如下所示的值列表，因为我使用 ToList() 函数将列转换为列表。

#the connection string
cnxn = pyodbc.connect(driver='{SQL Server}', server = 'NameOfTheServer',autocommit = True,uid ='name',pwd ='password')

cursor = cnxn.cursor()
params = ['3122145', '523532236']
sql = ("""
    SELECT  SO.column
    FROM    table AS SO
    WHERE SO.column = ?
    """)
cursor.executemany(sql, params)
row = cursor.fetchone()

即使我使用的是列表，executemany 函数也会引发错误： TypeError: ('Params must be in a list, tuple, or Row', 'HY000')

【问题讨论】：

戈德-汤普森，是的。这相当于在 WHERE 子句中使用 IN 关键字。

标签： pyodbc

【解决方案1】：

.executemany 不适用于 SELECT 语句。如果我们尝试，我们只会得到最后一行：

cnxn = pyodbc.connect(connection_string, autocommit=True)
crsr = cnxn.cursor()
crsr.execute("CREATE TABLE #tmp (id int primary key, txt varchar(10))")
crsr.execute(
    "INSERT INTO #tmp (id,txt) "
    "VALUES (1,'one'),(2,'two'),(3,'three'),(4,'four'),(5,'five')"
)
print(crsr.execute("SELECT * FROM #tmp").fetchall())
"""console output:
[(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four'), (5, 'five')]
"""
sql = "SELECT * FROM #tmp WHERE id = ?"
list_of_tuples = [(1,), (3,), (5,)]
crsr.executemany(sql, list_of_tuples)
print(crsr.fetchall())
"""console output:
[(5, 'five')]
"""
try:
    crsr.nextset()
    print(crsr.fetchall())
except pyodbc.ProgrammingError as pe:
    print(pe)
    """console output:
    No results.  Previous SQL was not a query.
    """

相反，我们需要构建一串参数占位符并在 IN 子句中使用它，如下所示：

tuple_of_scalars = tuple(x[0] for x in list_of_tuples)
sql = f"SELECT * FROM #tmp WHERE id IN ({','.join('?' * len(tuple_of_scalars))})"
print(sql)
"""console output:
SELECT * FROM #tmp WHERE id IN (?,?,?)
"""
crsr.execute(sql, tuple_of_scalars)
print(crsr.fetchall())
"""console output:
[(1, 'one'), (3, 'three'), (5, 'five')]
"""

【讨论】：