如您所说，这在sql中非常容易，那么为什么不在sql中这样做呢？
import pandas as pd
import sqlite3
#We'll use firelynx's tables:
presidents = pd.DataFrame({"name": ["Bush", "Obama", "Trump"],
"president_id":[43, 44, 45]})
terms = pd.DataFrame({'start_date': pd.date_range('2001-01-20', periods=5, freq='48M'),
'end_date': pd.date_range('2005-01-21', periods=5, freq='48M'),
'president_id': [43, 43, 44, 44, 45]})
war_declarations = pd.DataFrame({"date": [datetime(2001, 9, 14), datetime(2003, 3, 3)],
"name": ["War in Afghanistan", "Iraq War"]})
#Make the db in memory
conn = sqlite3.connect(':memory:')
#write the tables
terms.to_sql('terms', conn, index=False)
presidents.to_sql('presidents', conn, index=False)
war_declarations.to_sql('wars', conn, index=False)
qry = '''
select
start_date PresTermStart,
end_date PresTermEnd,
wars.date WarStart,
presidents.name Pres
from
terms join wars on
date between start_date and end_date join presidents on
terms.president_id = presidents.president_id
'''
df = pd.read_sql_query(qry, conn)
df：
PresTermStart PresTermEnd WarStart Pres
0 2001-01-31 00:00:00 2005-01-31 00:00:00 2001-09-14 00:00:00 Bush
1 2001-01-31 00:00:00 2005-01-31 00:00:00 2003-03-03 00:00:00 Bush
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