Question

我创建了一个带有学生表的数据库

myStr1 = "CREATE TABLE Students (reg_no VARCHAR(15), name VARCHAR(30), email VARCHAR(30), average_mark INTEGER, PRIMARY KEY(reg_no))"
         self.myCursor.execute(myStr1)

然后，我添加了一个函数，将学生详细信息添加到表中，并希望根据条件过滤掉某些记录。以下是我的代码：

def insert_student(self,reg_no,name,email,average_mark):
           self.reg_no = reg_no
           self.name = name
           self.email = email
           self.average_mark = average_mark 
           self.myCursor.execute("INSERT INTO Students VALUES (:reg_no, :name, :email, :average_mark)",{'reg_no':self.reg_no,'name':self.name,'email':self.email,'average_mark':self.average_mark})

           self.myConnection.commit()

def get_students(self,criteria = None):
          self.criteria = criteria
          self.myCursor.execute("SELECT * FROM Students WHERE '{}'".format(self.criteria))
          return self.myCursor.fetchall()

 myWrapper = DBWrapper()

 myWrapper.insert_student('F17/42770/2017','Mutheu Lorraine','mutheu@gmail.com',100)
 myWrapper.insert_student('F17/3030/2015','Ron Weasley', 'ron@eie.com',71) 
 myWrapper.insert_student('F17/3031/2015','Hermione Granger', 'hermine@eie.com',71) 
 myWrapper.insert_student('F17/3031/2017','Ginny Weasley', 'ginny@eie.com',71) 
 myWrapper.myConnection.commit()

 students = myWrapper.get_students('reg_no = F17/42770/2017')
 print(students)

然而，当我运行我的代码时，我只会得到＆＃39; []＆＃39;而不是具有给定注册号的学生的所有细节。我应该怎么做呢？

Answer 1

格式化后，生成的SQL命令为：

output=output[['Patient_ID','Physician','Hospital']]

整个WHERE子句是一个字符串，并且该字符串对于任何行都不会计算为true。

要使条件成为SQL表达式，请删除引号。但必须引用比较值，以便将其识别为字符串：

SELECT * FROM Students WHERE 'reg_no = F17/42770/2017'

使用特定条件从数据库过滤记录

1 个答案: