pandas pandas读sql查询和读sql表的区别
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时间：2020-09-14 05:02:03 来源:igfitidea点击:
difference between pandas read sql query and read sql table
提问by Oussama Jabri
Is there a difference in relation to time execution between this two commands :
这两个命令之间的时间执行是否存在差异：
import pandas as pd
df=pd.read_sql_query('SELECT * FROM TABLE',conn)
df=pd.read_sql_table(TABLE, conn)
Thank you for your help
感谢您的帮助
采纳答案by MaxU
I don't think you will notice this difference.
我不认为你会注意到这种差异。
Here is a source code for both functions:
这是两个函数的源代码：
In [398]: pd.read_sql_query??
Signature: pd.read_sql_query(sql, con, index_col=None, coerce_float=True, params=None, parse_dates=None, chunksize=None)
Source:
def read_sql_query(sql, con, index_col=None, coerce_float=True, params=None,
parse_dates=None, chunksize=None):
pandas_sql = pandasSQL_builder(con)
return pandas_sql.read_query(
sql, index_col=index_col, params=params, coerce_float=coerce_float,
parse_dates=parse_dates, chunksize=chunksize)
and
和
In [399]: pd.read_sql_table??
Signature: pd.read_sql_table(table_name, con, schema=None, index_col=None, coerce_float=True, parse_dates=None, columns=None, chunksize=None
)
Source:
def read_sql_table(table_name, con, schema=None, index_col=None,
coerce_float=True, parse_dates=None, columns=None,
chunksize=None):
con = _engine_builder(con)
if not _is_sqlalchemy_connectable(con):
raise NotImplementedError("read_sql_table only supported for "
"SQLAlchemy connectable.")
import sqlalchemy
from sqlalchemy.schema import MetaData
meta = MetaData(con, schema=schema)
try:
meta.reflect(only=[table_name], views=True)
except sqlalchemy.exc.InvalidRequestError:
raise ValueError("Table %s not found" % table_name)
pandas_sql = SQLDatabase(con, meta=meta)
table = pandas_sql.read_table(
table_name, index_col=index_col, coerce_float=coerce_float,
parse_dates=parse_dates, columns=columns, chunksize=chunksize)
if table is not None:
return table
else:
raise ValueError("Table %s not found" % table_name, con)
NOTE: i have iintentionally cut off docstrings...
注意：我故意切断了文档字符串...
