当我用变量替换硬编码值时，Python SQL 查询返回 "ORA-00936: missing expression"

Question

我有一个充满信息的数据库，我正在尝试编写一个 python 脚本来提取一些数据并将其组织成报告。这是我到目前为止所拥有的:

import cx_Oracle
import pandas as pd

conn = cx_Oracle.connect('REDACTED')
cursor = conn.cursor()

# Currently hard-coded to return single known motor number
cursor.execute('SELECT MOTORID FROM MOTORS WHERE SERIALNUM=804')
# Returns [(11)]
lMotorID = cursor.fetchall()

# Query Assessments for list of how long the motor had run when assessment was taken
cursor.execute("SELECT DISTINCT RUNHOURS FROM ASSESSMENTS WHERE MOTORID = %s \
               ORDER BY RUNHOURS" % lMotorID[0])
# Returns [(0), (0.91), (8), (25), ...]
lHours = cursor.fetchall()

# Query for number of installed sensors by senor type
cursor.execute("SELECT SENSTYP, COUNT(STATUS) FROM HEALTH LEFT JOIN INSTRUMENTATION \
               ON HEALTH.INSTROID = INSTRUMENTATION.INSTROID LEFT JOIN ASSESSMENTS \
               ON HEALTH.ASSESSID = ASSESSMENTS.ASSESSID WHERE ASSESSMENTS.ASSESSID \
               IN (SELECT ASSESSID FROM ASSESSMENTS WHERE MOTORID = 11 AND RUNHOURS = %s) \
               GROUP BY SENSTYP ORDER BY SENSTYP" % lHours[2])
# Returns a 2-column dataframe with sensor type in column 0 and the total in column 1
dfTotal = pd.DataFrame(cursor.fetchall())

因为我希望它适用于任何电机，所以我想用变量替换硬编码的 MOTORID = 11。我尝试用以下内容替换最后一个查询:

cursor.execute("SELECT SENSTYP, COUNT(STATUS) FROM HEALTH LEFT JOIN INSTRUMENTATION \
               ON HEALTH.INSTROID = INSTRUMENTATION.INSTROID LEFT JOIN ASSESSMENTS \
               ON HEALTH.ASSESSID = ASSESSMENTS.ASSESSID WHERE ASSESSMENTS.ASSESSID \
               IN (SELECT ASSESSID FROM ASSESSMENTS WHERE MOTORID = %s AND RUNHOURS = %s) \
               GROUP BY SENSTYP ORDER BY SENSTYP" % (lMotorID[0], lHours[2])) 
dfTotal = pd.DataFrame(cursor.fetchall())

就在那时我收到了 ORA-00936 错误。我不明白为什么查询是用硬编码值完成的，但当该值被变量(在上一个查询中起作用的变量)替换时却不是。提前致谢。

Answer 1

需要修复 cursor.execute 的语法，例如

cursor.execute('... WHERE MOTORID = :mt_id AND RUNHOURS = :run_hr', mt_id=lMotorID[0][0], run_hr=lHours[2][0])

在参数前添加百分号前缀对于通过 python 连接 MySQL 有效，而 Oracle 接受冒号。

或者另一个选项是使用有序元组:

cursor.execute('... WHERE MOTORID = :1 AND RUNHOURS = :2', (lMotorID[0][0],lHours[2][0]))