我想使用select语句从数据集中隔离出前525,600行,使用LIMIT语句很容易,但是我想对58个单独的表执行此操作。我有一个表名列表,正在尝试定义一个遍历所有表的函数,但是在sql语句中无法识别在函数中定义的变量名。这是我的代码:
import pandas as pd
from sqlalchemy import create_engine
import psycopg2
mylist = ['egauge13830','egauge13836','egauge13974','egauge14018','egauge14795','egauge15601',
'egauge15623','egauge16133','egauge16608','egauge16616','egauge17073','egauge17311',
'egauge18158','egauge18350','egauge18544','egauge19696','egauge19810','egauge19821',
'egauge20358','egauge20407','egauge20670','egauge20925','egauge21932','egauge22084',
'egauge22271','egauge22785','egauge23534','egauge24121','egauge24318','egauge2474',
'egauge26086','egauge26944','egauge27467','egauge28351','egauge28489','egauge2850',
'egauge2852','egauge28684','egauge30039','egauge30378','egauge3166','egauge3167',
'egauge3171','egauge32290','egauge32507','egauge33764','egauge3608','egauge3611',
'egauge4183','egauge5198','egauge6437','egauge7692','egauge7729','egauge7731',
'egauge8253','egauge8617','egauge8816','egauge9102']
def first_chunk(egauge):
engine = create_engine('postgresql://postgres:postgres@stargate/profiles')
start_time_stmnt = """
SELECT *
FROM egauge
LIMIT 525600
"""
first = pd.read_sql_query(start_time_stmnt, engine)
def iterthro(data):
for x in data:
first_chunk(x)
iterthro(mylist)
我收到的错误告诉我,“ egauge”关系不存在。顺便说一句,我知道这段代码是毫无用处的,因为它对选定的行没有任何作用,但是我打算对此做更多的事情,并希望在继续前进之前弄清楚这个问题。我已经尝试过一些简单的事情,例如引号的不同组合,但不确定是否犯了一个简单的语法错误,或者我的逻辑是否完全有缺陷。感谢您提供的所有帮助!
"{}".format(x)
在字符串中使用变量。希望对您有所帮助!def first_chunk(egauge):
engine = create_engine('postgresql://postgres:postgres@stargate/profiles')
start_time_stmnt = """
SELECT *
FROM {}
LIMIT 525600
""".format(egauge)
first = pd.read_sql_query(start_time_stmnt, engine)
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